Multilayer ceramic capacitor

ABSTRACT

A multilayer ceramic capacitor includes a multilayer unit, thickness-direction first and second outer layer sections, length-direction first and second outer layer sections, and width-direction first and second outer layer sections. A dimension of the thickness-direction second outer layer section is greater than a dimension of the thickness-direction first outer layer section. The thickness-direction second outer layer section includes an inner portion and an outer portion. A composition ratio of Si to Ti in a ceramic dielectric layer included in the outer portion is higher than that in the inner portion. A boundary portion between the outer portion and the inner portion has a larger Si content than the outer portion. The inner portion has a higher composition ratio of Mn to Ti than the outer portion. Each of minimum dimensions in the length direction of the length-direction first and second outer layer sections is greater than both dimensions in the width direction of the width-direction first and second outer layer sections.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer ceramic capacitor, and amultilayer ceramic capacitor array including a multilayer ceramiccapacitor.

2. Description of the Related Art

Generally, a capacitor device includes a body constituted by alternatelystacking inner electrode layers and dielectric layers and outerelectrodes disposed on the outer surfaces of the body. In a multilayerceramic capacitor, the dielectric layers are constituted by a ceramicdielectric material.

Generally, the body of a multilayer ceramic capacitor is formed asfollows. The body contains a multilayer unit having a substantiallyrectangular parallelepiped shape and formed by alternately and denselystacking a plurality of conductive layers, which serve as innerelectrode layers, and a plurality of ceramic dielectric layers. Outerlayer sections constituted by ceramic dielectric layers and outer layersections constituted by ceramic dielectric layers and a relatively smallnumber of conductive layers disposed within the ceramic dielectriclayers cover the multilayer unit.

In the above-described multilayer ceramic capacitor, the occurrence ofcracks in the above-described ceramic dielectric layers may be observed.The occurrence of cracks reduces the reliability of a multilayer ceramiccapacitor as a product or decreases the yield in a manufacturingprocess.

An example of a technique for reducing the occurrence of cracks in amultilayer ceramic capacitor is disclosed in Japanese Unexamined PatentApplication Publication No. 2012-248581. In this multilayer ceramiccapacitor, a pair of outer layer sections constituted by ceramicdielectric layers that sandwich the above-described multilayer unittherebetween in the stacking direction is provided. In this pair ofouter layer sections, one outer layer section that defines the principalsurface of the multilayer unit to be mounted on a wiring board isthicker than the other outer layer section.

In this multilayer ceramic capacitor, it is possible to reduce theoccurrence of cracks caused by an external stress which is applied tothe multilayer ceramic capacitor when the wiring board having themultilayer ceramic capacitor mounted thereon is deflected due to anexternal force.

However, as a result of conducting an extensive study, the presentinventors have discovered the following fact concerning theabove-described multilayer ceramic capacitor. If the thickness of theabove-described other outer layer section is increased or if thethickness of the above-described multilayer unit is increased, cracksoccur at the boundary between the multilayer unit and the outer layersection when the body of the multilayer ceramic capacitor is subjectedto firing. Unlike the above-described cracks due to an external stress,this type of crack may occur due to an internal stress produced by thedifference in the coefficients of thermal shrinkage between the ceramicdielectric layers and the conductive layers when the body of themultilayer ceramic capacitor is subjected to firing.

SUMMARY OF THE INVENTION

Various preferred embodiments of the present invention has beendeveloped based on the above-described findings. Accordingly, variouspreferred embodiments of the present invention provide a multilayerceramic capacitor in which it is possible to significantly reduce orprevent the occurrence of cracks caused by an internal stress producedby a difference in coefficient of thermal shrinkage between a ceramicdielectric layer and a conductive layer, and a multilayer ceramiccapacitor array including this multilayer ceramic capacitor and amultilayer ceramic capacitor mount body including this multilayerceramic capacitor.

According to a preferred embodiment of the present invention, amultilayer ceramic capacitor includes a body including conductive layersand ceramic dielectric layers alternately stacked on each other in athickness direction, and a plurality of outer electrodes disposed onportions of the body, wherein the body includes first and secondprincipal surfaces opposing each other in the thickness direction, firstand second end surfaces opposing each other in a length direction, andfirst and second side surfaces opposing each other in a width direction,the plurality of outer electrodes includes a first outer electrodecovering at least the first end surface and a second outer electrodecovering at least the second end surface, some of the conductive layersinclude a first effective portion and a first extension portionextending from the first effective portion toward the first end surfaceand connecting to the first outer electrode, and others of theconductive layers include a second effective portion and a secondextension portion extending from the second effective portion toward thesecond end surface and connecting to the second outer electrode, thebody includes a multilayer unit including an effective portion definedby the first and second effective portions and portions of the ceramicdielectric layers stacked therebetween, the body is sectioned in thethickness direction into a thickness-direction first outer layer sectionthat includes one of the ceramic dielectric layers including the firstprincipal surface, a thickness-direction second outer layer section thatincludes one of the ceramic dielectric layers including the secondprincipal surface, and a thickness-direction inner layer section thatincludes the multilayer unit and that is disposed between thethickness-direction first and second outer layer sections, the body issectioned in the length direction into a length-direction first outerlayer section that includes the first extension portions and portions ofthe ceramic dielectric layers sandwiched by the first extension portionsand that defines the first end surface, a length-direction second outerlayer section that includes the second extension portions and portionsof the ceramic dielectric layers sandwiched by the second extensionportions and that defines the second end surface, and a length-directioninner layer section that includes the multilayer unit and that isdisposed between the length-direction first and second outer layersections, the body is sectioned in the width direction into awidth-direction first outer layer section that includes a portionbetween the first side surface and the multilayer unit, awidth-direction second outer layer section that includes a portionbetween the second side surface and the multilayer unit, and awidth-direction inner layer section that includes the multilayer unitand that is disposed between the width-direction first and second outerlayer sections, a dimension of the thickness-direction second outerlayer section in the thickness direction is greater than a dimension ofthe thickness-direction first outer layer section in the thicknessdirection, the ceramic dielectric layers included in thethickness-direction inner layer section and the thickness-directionfirst and second outer layer sections contains barium titanate and Si,the thickness-direction second outer layer section includes an outerportion which includes the second principal surface and an inner portiondisposed between the thickness-direction inner layer section and theouter portion, a composition ratio of Si to Ti in one of the ceramicdielectric layers included in the outer portion is higher than acomposition ratio of Si to Ti in one of the ceramic dielectric layersincluded in the inner portion, a boundary portion between the outerportion and the inner portion has a larger Si content than the outerportion, the inner portion has a higher composition ratio of Mn to Tithan the outer portion, and each of minimum dimensions in the lengthdirection of the length-direction first and second outer layer sectionsis greater than both minimum dimensions in the width direction of thewidth-direction first and second outer layer sections.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of rare earth element to Ti than the outer portion.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of Dy to Ti than the outer portion.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that adimension of the outer portion in the thickness direction is greaterthan a dimension of the inner portion in the thickness direction.

According to another preferred embodiment of the present invention, amultilayer ceramic capacitor includes a body including conductive layersand ceramic dielectric layers alternately stacked on each other in athickness direction, and a plurality of outer electrodes disposed onportions of the body, wherein the body includes first and secondprincipal surfaces opposing each other in the thickness direction, firstand second end surfaces opposing each other in a length direction, andfirst and second side surfaces opposing each other in a width direction,the plurality of outer electrodes includes a first outer electrodecovering at least the first end surface and a second outer electrodecovering at least the second end surface, some of the conductive layersinclude a first effective portion and a first extension portionextending from the first effective portion toward the first end surfaceand connecting to the first outer electrode, and others of theconductive layers include a second effective portion and a secondextension portion extending from the second effective portion toward thesecond end surface and connecting to the second outer electrode, thebody includes a multilayer unit including an effective portion definedby the first and second effective portions and portions of the ceramicdielectric layers stacked therebetween, the body is sectioned in thethickness direction into a thickness-direction first outer layer sectionthat includes one of the ceramic dielectric layers including the firstprincipal surface, a thickness-direction second outer layer section thatincludes one of the ceramic dielectric layers including the secondprincipal surface, and a thickness-direction inner layer section thatincludes the multilayer unit and that is disposed between thethickness-direction first and second outer layer sections, the body issectioned in the length direction into a length-direction first outerlayer section that includes the first extension portions and portions ofthe ceramic dielectric layers sandwiched by the first extension portionsand that defines the first end surface, a length-direction second outerlayer section that includes the second extension portions and portionsof the ceramic dielectric layers sandwiched by the second extensionportions and that defines the second end surface, and a length-directioninner layer section that includes the multilayer unit and that isdisposed between the length-direction first and second outer layersections, the body is sectioned in the width direction into awidth-direction first outer layer section that includes a portionbetween the first side surface and the multilayer unit, awidth-direction second outer layer section that includes a portionbetween the second side surface and the multilayer unit, and awidth-direction inner layer section that includes the multilayer unitand that is disposed between the width-direction first and second outerlayer sections, a dimension of the thickness-direction second outerlayer section in the thickness direction is greater than a dimension ofthe thickness-direction first outer layer section in the thicknessdirection, the ceramic dielectric layers included in thethickness-direction inner layer section and the thickness-directionfirst and second outer layer sections contains barium titanate and Si,the thickness-direction second outer layer section includes an outerportion which includes the second principal surface and an inner portiondisposed between the thickness-direction inner layer section and theouter portion, a composition ratio of Si to Ti in one of the ceramicdielectric layers included in the outer portion is higher than acomposition ratio of Si to Ti in one of the ceramic dielectric layersincluded in the inner portion, a boundary portion between the outerportion and the inner portion has a larger Si content than the outerportion, the inner portion has a higher composition ratio of Mn to Tithan the outer portion, and each of minimum dimensions in the lengthdirection of the length-direction first and second outer layer sectionsis more than about 1.15 times as large as both minimum dimensions in thewidth direction of the width-direction first and second outer layersections.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of rare earth element to Ti than the outer portion.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of Dy to Ti than the outer portion.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that adimension of the outer portion in the thickness direction is greaterthan a dimension of the inner portion in the thickness direction.

According to a further preferred embodiment of the present invention, amultilayer ceramic capacitor includes a body including conductive layersand ceramic dielectric layers alternately stacked on each other in athickness direction, and a plurality of outer electrodes disposed onportions of the body, wherein the body includes first and secondprincipal surfaces opposing each other in the thickness direction, firstand second end surfaces opposing each other in a length direction, andfirst and second side surfaces opposing each other in a width direction,the plurality of outer electrodes includes a first outer electrodecovering at least the first end surface and a second outer electrodecovering at least the second end surface, some of the conductive layersinclude a first effective portion and a first extension portionextending from the first effective portion toward the first end surfaceand connecting to the first outer electrode, and others of theconductive layers include a second effective portion and a secondextension portion extending from the second effective portion toward thesecond end surface and connecting to the second outer electrode, thebody includes a multilayer unit including an effective portion definedby the first and second effective portions and portions of the ceramicdielectric layers stacked therebetween, the body is sectioned in thethickness direction into a thickness-direction first outer layer sectionthat includes one of the ceramic dielectric layers including the firstprincipal surface, a thickness-direction second outer layer section thatincludes one of the ceramic dielectric layers including the secondprincipal surface, and a thickness-direction inner layer section thatincludes the multilayer unit and that is disposed between thethickness-direction first and second outer layer sections, the body issectioned in the length direction into a length-direction first outerlayer section that includes the first extension portions and portions ofthe ceramic dielectric layers sandwiched by the first extension portionsand that defines the first end surface, a length-direction second outerlayer section that includes the second extension portions and portionsof the ceramic dielectric layers sandwiched by the second extensionportions and that defines the second end surface, and a length-directioninner layer section that includes the multilayer unit and that isdisposed between the length-direction first and second outer layersections, the body is sectioned in the width direction into awidth-direction first outer layer section that includes a portionbetween the first side surface and the multilayer unit, awidth-direction second outer layer section that includes a portionbetween the second side surface and the multilayer unit, and awidth-direction inner layer section that includes the multilayer unitand that is disposed between the width-direction first and second outerlayer sections, a dimension of the thickness-direction second outerlayer section in the thickness direction is greater than a dimension ofthe thickness-direction first outer layer section in the thicknessdirection, the ceramic dielectric layers included in thethickness-direction inner layer section and the thickness-directionfirst and second outer layer sections contains barium titanate and Si,the thickness-direction second outer layer section includes an outerportion which includes the second principal surface and an inner portiondisposed between the thickness-direction inner layer section and theouter portion, a composition ratio of Si to Ti in one of the ceramicdielectric layers included in the outer portion is higher than acomposition ratio of Si to Ti in one of the ceramic dielectric layersincluded in the inner portion, a boundary portion between the outerportion and the inner portion has a larger Si content than the outerportion, the inner portion has a higher composition ratio of Mn to Tithan the outer portion, each of minimum dimensions in the lengthdirection of the length-direction first and second outer layer sectionsis greater than both minimum dimensions in the width direction of thewidth-direction first and second outer layer sections, one of the firstand second extension portions of a first outermost conductive layer ofthe conductive layers that is closest to the first principal surface isinclined toward the second principal surface, one of the first andsecond extension portions of a second outermost conductive layer of theconductive layers that is closest to the second principal surface isinclined toward the first principal surface, and an amount ofinclination of the second outermost conductive layer is greater than anamount of inclination of the first outermost conductive layer.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that adifference between the amount of inclination of the second outermostconductive layer and the amount of inclination of the first outermostconductive layer is greater than a thickness of the dielectric layerstacked between the conductive layers.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of rare earth element to Ti than the outer portion.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of Dy to Ti than the outer portion.

In the above-described multilayer ceramic capacitor according to apreferred embodiment of the present invention, it is preferable that adimension of the outer portion in the thickness direction is greaterthan a dimension of the inner portion in the thickness direction

According to various preferred embodiments of the present invention, itis possible to provide a multilayer ceramic capacitor in which it ispossible to significantly reduce or prevent the occurrence of crackscaused by an internal stress produced by the difference in thecoefficient of thermal shrinkage between a ceramic dielectric layer anda conductive layer, and to provide a multilayer ceramic capacitor arrayincluding this multilayer ceramic capacitor and a multilayer ceramiccapacitor mount body including this multilayer ceramic capacitor.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating a multilayer ceramiccapacitor according to a first preferred embodiment of the presentinvention.

FIGS. 2 and 3 are schematic sectional views taken along lines II-II andIII-III, respectively, of FIG. 1.

FIGS. 4 and 5 are schematic sectional views taken along lines IV-IV andV-V, respectively, of FIG. 2.

FIG. 6 is a flowchart illustrating a manufacturing flow for themultilayer ceramic capacitor shown in FIG. 1.

FIG. 7 an exploded perspective view illustrating a multilayer structureof a set of base sheets, which define a body of the multilayer ceramiccapacitor shown in FIG. 1.

FIGS. 8A through 9B are schematic sectional views illustrating a step offixing a set of material sheets with pressure in the manufacturing flowshown in FIG. 6.

FIG. 10 is a schematic sectional view illustrating a multilayer ceramiccapacitor mount body of the first preferred embodiment of the presentinvention.

FIG. 11 is a plan view illustrating a multilayer ceramic capacitor arrayof the first preferred embodiment of the present invention.

FIG. 12 is a schematic sectional view taken along line XII-XII of FIG.11.

FIG. 13 is a schematic perspective view illustrating a multilayerceramic capacitor according to a second preferred embodiment of thepresent invention.

FIGS. 14 and 15 are schematic sectional views taken along lines XIV-XIVand XV-XV, respectively, of FIG. 13.

FIGS. 16 and 17 are schematic sectional views illustrating a multilayerceramic capacitor according to a modified example of the secondpreferred embodiment of the present invention.

FIG. 18 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 1 through 7 in a firstverification test.

FIG. 19 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 8 through 14 in a secondverification test.

FIG. 20 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 15 through 35 in a thirdverification test.

FIG. 21 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 36 through 39 in a fourthverification test.

FIG. 22 is a schematic view illustrating a method for deflecting awiring board having a multilayer ceramic capacitor mounted thereon inthe fourth verification test.

FIG. 23 illustrates an example of an enlarged image of a cross sectionof a multilayer ceramic capacitor observed with a scanning electronmicroscope (SEM).

FIG. 24 is a schematic sectional view illustrating a multilayer ceramiccapacitor according to a modification of the second preferred embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowin detail with reference to the accompanying drawings. In the followingpreferred embodiments, the same or similar components are designated bylike reference numerals, and components designated by like referencenumerals will be explained only once.

First Preferred Embodiment

FIG. 1 is a schematic perspective view illustrating a multilayer ceramiccapacitor 1A according to a first preferred embodiment of the presentinvention. FIGS. 2 and 3 are schematic sectional views taken along linesII-II and III-III, respectively, of FIG. 1. FIGS. 4 and 5 are schematicsectional views taken along lines IV-IV and V-V, respectively, of FIG.2. The configuration of the multilayer ceramic capacitor 1A of the firstpreferred embodiment will first be described below with reference toFIGS. 1 through 5.

As shown in FIGS. 1 through 5, the multilayer ceramic capacitor 1A is anelectronic component preferably having a rectangular or substantiallyrectangular parallelepiped shape and including a body 2 and first andsecond outer electrodes 5 a and 5 b, which define a pair of outerelectrodes.

As shown in FIGS. 2 through 5, the body 2 preferably has a rectangularor substantially rectangular parallelepiped shape and includes ceramicdielectric layers 3 and inner electrode layers 4 alternately stacked oneach other in a predetermined direction. The inner electrode layers 4define and serve as conductive layers. The term “rectangularparallelepiped” includes a rectangular parallelepiped having a roundedportion at a corner or a ridge of the body 2 and a rectangularparallelepiped having a step portion or uneven portion, which isnegligible as a whole, on the surface of the body 2.

The ceramic dielectric layers 3 contain a perovskite compound expressedby ABO₃ (“A” contains Ba and “B” contains Ti) as a principal component.A typical example of a perovskite compound expressed by ABO₃ is bariumtitanate (BaTiO₃).

The ceramic dielectric layers 3 contain Si as a secondary component. Siis contained in the ceramic dielectric layers 3 by adding a Si compound,such as glass or SiO₂, to a perovskite compound expressed by ABO₃.Another compound, such as a Mn compound, an Mg compound, a Co compound,a Ni compound, or a rare earth compound, may be added to a perovskitecompound expressed by ABO₃.

In the first preferred embodiment, the principal component of theceramic dielectric material for the ceramic dielectric layers 3 is notrestricted to a perovskite compound expressed by ABO₃ (“A” contains Baand “B” contains Ti). Another ceramic dielectric material having a highdielectric constant containing, for example, calcium titanate, strontiumtitanate, or calcium zirconate as a principal component, may be used.

As a material for the inner electrode layers 4, a metal, such as Ni, Cu,Ag, Pd, or Au, or an alloy containing at least one of such metals (forexample, an alloy of Ag and Pd) may be used, for example. The thicknessof each inner electrode layer 4 after the body 2 has been fired ispreferably about 0.3 μm to about 2 μm, for example.

The body 2 is preferably fabricated in the following manner. A pluralityof material sheets, that is, a plurality of ceramic green sheets, whichwill form the ceramic dielectric layers 3, on which conductor patterns,which will form the inner electrode layers 4, are printed, are firstprepared. These material sheets are stacked on and pressed against eachother so as to form a mother block. Then, the mother block is cut into aplurality of chips, and they are fired. Each of the plurality of chipsserves as the body 2. Details of this fabrication process will bediscussed later.

As shown in FIGS. 1 through 5, the first and second outer electrodes 5 aand 5 b are disposed separately from each other such that they coverouter surfaces of the body 2 which are positioned at both end portionsthereof in a predetermined direction. The first and second outerelectrodes 5 a and 5 b each include a conductive film.

The first and second outer electrodes 5 a and 5 b each include afoundation layer which covers the above-described end portions of thebody 2 and a plated layer which covers the foundation layer. As amaterial for the foundation layer, a metal, such as Ni, Cu, Ag, Pd, orAu, or an alloy containing at least one of such metals (for example, analloy of Ag and Pd) may be used, for example. The thickness of thefoundation layer is preferably about 10 μm to about 50 μm, for example.

The foundation layer may be formed by burning a conductor paste appliedto the above-described end portions of the body 2 which has been fired.Alternatively, the foundation layer may be formed by firing, togetherwith the inner electrode layers 4, a conductor paste applied to theabove-described end portions of the body 2 which has not been fired.Alternatively, the foundation layer may be formed by plating theabove-described end portions of the body 2 or by curing a thermosettingresin containing a metal applied to the end portions of the body 2.

If the foundation layer contains a resin, it is possible to reduce aload on the body 2 caused by an external stress which is produced when amounting member (for example, a wiring board 101, which will bediscussed later) having the multilayer ceramic capacitor 1A mountedthereon is deflected due to an external force. This makes it possible toreduce the occurrence of cracks in the body 2.

As a material for the plated layer, a metal, such as Ni, Sn, Cu, Ag, Pd,or Au, or an alloy containing at least one of such metals (for example,an alloy of Ag and Pd) may be used, for example.

The plated layer may be constituted by a plurality of layers, forexample. In this case, the plated layer is preferably a two-layerstructure in which a Sn plated layer is provided on a Ni plated layer.In this case, the Ni plated layer functions as a solder barrier layer,while the Sn plated layer improves solder wettability. The thickness ofone plated layer is preferably about 1.0 μm to about 10 μm, for example.

As shown in FIGS. 2, 4, and 5, if it is assumed that two inner electrodelayers 4 adjacent to each other with a ceramic dielectric layer 3therebetween in the stacking direction define a pair, one innerelectrode layer 4 is connected to the first outer electrode 5 a via afirst extension portion 4 c 1 within the multilayer ceramic capacitor1A, while the other inner electrode layer 4 is connected to the secondouter electrode 5 b via a second extension portion 4 c 2 within themultilayer ceramic capacitor 1A. The plurality of inner electrode layers4 preferably are all rectangular or substantially rectangular, as viewedfrom above.

In the multilayer ceramic capacitor 1A of the first preferred embodimentconfigured as described above, a plurality of capacitor elements areelectrically connected in parallel between the first and second outerelectrodes 5 a and 5 b. The first extension portion 4 c 1 is a portionpositioned between an effective portion of the inner electrode layers 4(that is, an area where a plurality of inner electrode layers 4 arestacked in the stacking direction) and the first outer electrode 5 a,while the second extension portion 4 c 2 is a portion positioned betweenthe effective portion of the inner electrode layers 4 and the secondouter electrode 5 b. The effective portion of the inner electrode layers4 will be discussed later.

In the first preferred embodiment, preferably all the conductive layers,that is, all the inner electrode layers 4, inside the body 2 areconnected to one of the first and second outer electrodes 5 a and 5 b.However, the multilayer ceramic capacitor 1A may be configured in adifferent manner as long as at least some of the plurality of conductivelayers are connected to the first outer electrode 5 a and at least someof the remaining conductive layers are connected to the second outerelectrode 5 b. That is, there may be some conductive layers that areneither connected to the first outer electrode 5 a nor the second outerelectrode 5 b.

As shown in FIGS. 2 and 3, in the multilayer ceramic capacitor 1A of thefirst preferred embodiment, the inner electrode layers 4 other thanthose defining the first and second extension portions 4 c 1 and 4 c 2define the effective portion that determines the electrostaticcapacitance of the multilayer ceramic capacitor 1A. The effectiveportion of the inner electrode layers 4 and the ceramic dielectriclayers 3 positioned between the inner electrode layers 4 defines amultilayer unit 10. The multilayer unit 10 is formed preferably bydensely stacking the ceramic dielectric layers 3 and the inner electrodelayers 4 in the thickness direction, for example.

By referring to FIGS. 1 through 5, as the orientations of the multilayerceramic capacitor 1A, the stacking direction of the ceramic dielectriclayers 3 and the inner electrode layers 4 will be defined as a thicknessdirection T, the direction in which the first and second outerelectrodes 5 a and 5 b are arranged side by side perpendicular to thethickness direction T is defined as a length direction L, and thedirection perpendicular to both of the thickness direction T and thelength direction L is defined as a width direction W. In the followingdescription, these terms will be used.

By referring to FIGS. 2 through 5, among six outer surfaces of the body2, a pair of outer surfaces opposing each other in the thicknessdirection T will be defined as first and second principal surfaces 2 a 1and 2 a 2, a pair of outer surfaces opposing each other in the lengthdirection L will be defined as first and second end surfaces 2 b 1 and 2b 2, and a pair of outer surfaces opposing each other in the widthdirection W will be defined as first and second side surfaces 2 c 1 and2 c 2. In the following description, these terms will be used.

As shown in FIGS. 1 through 5, the first and second outer electrodes 5 aand 5 b are disposed such that they cover outer surfaces of the body 2which are positioned in the length direction L. More specifically, thefirst outer electrode 5 a is disposed such that it covers the first endsurface 2 b 1 and also covers portions of the first and second principalsurfaces 2 a 1 and 2 a 2 and the first and second side surfaces 2 c 1and 2 c 2 positioned closer to the first end surface 2 b 1, while thesecond outer electrode 5 b is disposed such that it covers the secondend surface 2 b 2 and also covers portions of the first and secondprincipal surfaces 2 a 1 and 2 a 2 and the first and second sidesurfaces 2 c 1 and 2 c 2 positioned closer to the second end surface 2 b2.

As shown in FIGS. 2 and 3, the body 2 is sectioned in the thicknessdirection T into a thickness-direction inner layer section 6 a andthickness-direction first and second outer layer sections 6 b 1 and 6 b2.

The thickness-direction inner layer section 6 a includes the multilayerunit 10 and is constituted by the inner electrode layers 4 and ceramicdielectric layers 3. The inner electrode layers 4 defining thethickness-direction inner layer section 6 a include the inner electrodelayers 4 contained in the multilayer unit 10, the inner electrode layers4 defining the first extension portion 4 c 1 which extends from some ofthe inner electrode layers 4 contained in the multilayer unit 10 towardthe first end surface 2 b 1 so as to be connected to the first outerelectrode 5 a, and the inner electrode layers 4 defining the secondextension portion 4 c 2 which extends from the remaining inner electrodelayers 4 contained in the multilayer unit 10 toward the second endsurface 2 b 2 so as to be connected to the second outer electrode 5 b.

The thickness-direction first outer layer section 6 b 1 is constitutedby a ceramic dielectric layer 3 and does not include any inner electrodelayer 4. The thickness-direction first outer layer section 6 b 1 coversthe surface of the thickness-direction inner layer section 6 a closer tothe first principal surface 2 a 1 so as to define the first principalsurface 2 a 1 of the body 2.

The thickness-direction second outer layer section 6 b 2 is constitutedby a ceramic dielectric layer 3 and does not include any inner electrodelayer 4. The thickness-direction second outer layer section 6 b 2 coversthe surface of the thickness-direction inner layer section 6 a closer tothe second principal surface 2 a 2 so as to define the second principalsurface 2 a 2 of the body 2.

With this configuration, the thickness-direction inner layer section 6 ais sandwiched between the thickness-direction first and second outerlayer sections 6 b 1 and 6 b 2 in the thickness direction T. Among theinner electrode layers 4 contained in the thickness-direction innerlayer section 6 a, the first conductive layer 4 a disposed closest tothe first principal surface 2 a 1 is disposed adjacent to the ceramicdielectric layer 3 defining the thickness-direction first outer layersection 6 b 1. Among the inner electrode layers 4 contained in thethickness-direction inner layer section 6 a, the second conductive layer4 b disposed closest to the second principal surface 2 a 2 is disposedadjacent to the ceramic dielectric layer 3 defining thethickness-direction second outer layer section 6 b 2.

As shown in FIGS. 2, 4, and 5, the body 2 is sectioned in the lengthdirection L into a length-direction inner layer section 7 a andlength-direction first and second outer layer sections 7 b 1 and 7 b 2.

The length-direction inner layer section 7 a includes the multilayerunit 10 and is constituted by the inner electrode layers 4 and ceramicdielectric layers 3. The inner electrode layers 4 defining thelength-direction inner layer section 7 a are constituted only by theinner electrode layers 4 contained in the multilayer unit 10.

The length-direction first outer layer section 7 b 1 is constituted bythe inner electrode layers 4 defining the first extension portion 4 c 1and portions of the ceramic dielectric layers 3. The length-directionfirst outer layer section 7 b 1 covers the surface of thelength-direction inner layer section 7 a closer to the first end surface2 b 1 so as to define the first end surface 2 b 1 of the body 2.

The length-direction second outer layer section 7 b 2 is constituted bythe inner electrode layers 4 defining the second extension portion 4 c 2and portions of the ceramic dielectric layers 3. The length-directionsecond outer layer section 7 b 2 covers the surface of thelength-direction inner layer section 7 a closer to the second endsurface 2 b 2 so as to define the second end surface 2 b 2 of the body2.

With this configuration, the length-direction inner layer section 7 a issandwiched between the length-direction first and second outer layersections 7 b 1 and 7 b 2 in the length direction L.

As shown in FIGS. 3 through 5, the body 2 is sectioned in the widthdirection W into a width-direction inner layer section 8 a andwidth-direction first and second outer layer sections 8 b 1 and 8 b 2.

The width-direction inner layer section 8 a includes the multilayer unit10 and is constituted by the inner electrode layers 4 and ceramicdielectric layers 3. The inner electrode layers 4 defining thewidth-direction inner layer section 8 a include the inner electrodelayers 4 contained in the multilayer unit 10 and the inner electrodelayers 4 defining the first and second extension portions 4 c 1 and 4 c2.

The width-direction first outer layer section 8 b 1 is constituted by aceramic dielectric layer 3 and does not include any inner electrodelayer 4. The width-direction first outer layer section 8 b 1 covers thesurface of the width-direction inner layer section 8 a closer to thefirst side surface 2 c 1 so as to define the first side surface 2 c 1 ofthe body 2.

The width-direction second outer layer section 8 b 2 is constituted by aceramic dielectric layer 3 and does not include any inner electrodelayer 4. The width-direction second outer layer section 8 b 2 covers thesurface of the width-direction inner layer section 8 a closer to thesecond side surface 2 c 2 so as to define the second side surface 2 c 2of the body 2.

With this configuration, the width-direction inner layer section 8 a issandwiched between the width-direction first and second outer layersections 8 b 1 and 8 b 2 in the width direction W.

In this manner, in the multilayer ceramic capacitor 1A of the firstpreferred embodiment, the multilayer unit 10 formed preferably byalternately and densely stacking the plurality of inner electrode layers4 and the plurality of ceramic dielectric layers 3 is contained in thebody 2. Outer layer sections constituted by ceramic dielectric layers 3(that is, the thickness-direction first and second outer layer sections6 b 1 and 6 b 2 and the width-direction first and second outer layersections 8 b 1 and 8 b 2) and outer layer sections constituted byportions of ceramic dielectric layers 3 and portions of a relativelysmall number of inner electrode layers 4 which are disposed between theceramic dielectric layers 3 (that is, the length-direction first andsecond outer layer sections 7 b 1 and 7 b 2) are disposed such that theycover the multilayer unit 10. With this arrangement, the body 2 isprovided.

As shown in FIG. 3, in the multilayer ceramic capacitor 1A of the firstpreferred embodiment, a dimension T1 of the multilayer unit 10 in thethickness direction T is preferably greater than a dimension W1 of themultilayer unit 10 in the width direction W (T1>W1). With thisconfiguration, it is possible to provide a large multilayer unit 10without increasing the dimension W1 in the width direction W. This makesit possible to increase the number of ceramic dielectric layers 3 andinner electrode layers 4 to be stacked in the thickness direction T.Thus, without increasing the size of the multilayer ceramic capacitor 1Ain the width direction W (in other words, without increasing the arearequired for mounting the multilayer ceramic capacitor 1A), theelectrostatic capacitance of the multilayer ceramic capacitor 1A isincreased.

As shown in FIG. 2, in the multilayer ceramic capacitor 1A of the firstpreferred embodiment, a dimension L1 of the multilayer unit 10 in thelength direction L is preferably greater than the dimension T1 of themultilayer unit 10 in the thickness direction T (L1>T1). The reason forthis is as follows. It is necessary to separate the first and secondouter electrodes 5 a and 5 b from each other by a considerable distancein the length direction L to secure insulation characteristicstherebetween, which inevitably increases the dimension L1 of themultilayer unit 10 in the length direction L. Even if the number ofceramic dielectric layers 3 and inner electrode layers 4 is decreased inthe thickness direction T for the sake of the increased dimension L ofthe multilayer unit 10 in the length direction L, a considerable amountof electrostatic capacitance is secured.

As shown in FIGS. 2 and 3, in the multilayer ceramic capacitor 1A of thefirst preferred embodiment, a dimension T0 of the body 2 in thethickness direction T is preferably greater than a dimension W0 of thebody 2 in the width direction W (T0>W0), and also, a dimension L0 of thebody 2 in the length direction L is preferably greater than thedimension T0 of the body 2 in the thickness direction T (L0>T0). Thereason for setting the relationships among the dimensions of the body 2in this manner is to reduce the size of the multilayer ceramic capacitor1A to a minimal level to implement high-density mounting. A largestpossible size of the multilayer unit 10 is first secured, and then, itis necessary to minimize the sizes of various outer layer sections (thatis, the above-described thickness-direction first and second outer layersections 6 b 1 and 6 b 2, length-direction first and second outer layersections 7 b 1 and 7 b 2, and width-direction first and second outerlayer sections 8 b 1 and 8 b 2). To implement this, the relationshipsamong the outer dimensions of the body 2 are preferably the same asthose of the multilayer unit 10.

As shown in FIGS. 2 and 3, a dimension t2 of the thickness-directionsecond outer layer section 6 b 2 in the thickness direction T is greaterthan a dimension t1 of the thickness-direction first outer layer section6 b 1 in the thickness direction T (t2>t1). With this configuration, themultilayer ceramic capacitor 1A can be mounted on a mounting member,such as a wiring board, such that the second principal surface 2 a 2defined by the thickness-direction second outer layer section 6 b 2faces the mounting member. Thus, even if the mounting member isdeflected due to an external force, it is possible to significantlyreduce or prevent the occurrence of cracks caused by an external stressapplied to the multilayer ceramic capacitor 1A.

As discussed above, generally, in a multilayer ceramic capacitor, acrack may be produced in a ceramic dielectric layer because an internalstress produced by the difference in the coefficients of thermalshrinkage between ceramic dielectric layers and conductive layers actsas a shear stress on the ceramic dielectric layer.

Concerning the width direction, this type of crack is likely to beproduced mostly at a boundary between a width-direction inner layersection and a width-direction first or second outer layer section, inwhich case, a crack is produced in an area starting from a widthwise endportion of the multilayer unit to the surface of the body near thiswidthwise end portion.

Concerning the length direction, this type of crack is likely to beproduced mostly at a boundary between a length-direction inner layersection and a length-direction first or second outer layer section, inwhich case, a crack is produced in an area starting from a longitudinalend portion of the multilayer unit to the surface of the body near thislongitudinal end portion. Concerning the length direction, inparticular, this type of crack is also likely to be produced at aboundary between an extension portion of a conductive layer contained inthe length-direction first or second outer layer section and a ceramicdielectric layer adjacent to this extension portion. This crack is alsoreferred to as “interlayer delamination”.

These cracks are produced particularly when the dimension t2 of thethickness-direction second outer layer section 6 b 2 in the thicknessdirection T is greater than the dimension t1 of the thickness-directionfirst outer layer section 6 b 1 in the thickness direction T, as in thecase of the first preferred embodiment of the present invention.

As a result of conducting an extensive study, the present inventors havediscovered that the occurrence of such a crack caused by an internalstress produced by the difference in the coefficients of thermalshrinkage between ceramic dielectric layers and conductive layers iscapable of being significantly reduced or prevented by increasing anadhesion force of a ceramic dielectric material in the width-directionfirst and second outer layer sections and that in the length-directionfirst and second outer layer sections and/or by increasing an adhesionforce between the ceramic dielectric material and a conductor materialin the length-direction first and second outer layer sections. Then, thepresent inventors have discovered that, in order to implement this, in astep of pressing a set of material sheets (S5) in a manufacturing flow(see FIG. 6) of multilayer ceramic capacitors in the first preferredembodiment, the application of a sufficient pressure force to portionswhich will define the width-direction first and second outer layersections 8 b 1 and 8 b 2 and the length-direction first and second outerlayer sections 7 b 1 and 7 b 2 is effective.

As a result, the present inventors have discovered that, in amanufactured multilayer ceramic capacitor, if certain ones of thefollowing conditions are satisfied, the occurrence of cracks caused byan internal stress is effectively reduced or prevented and thereliability of multilayer ceramic capacitors as products and the yieldin a manufacturing process is greatly improved. These conditions havebeen established on the basis of evaluation results of first and secondverification tests, which will be discussed below.

As shown in FIG. 3, both of dimensions w1 and w2 of the width-directionfirst and second outer layer sections 8 b 1 and 8 b 2, respectively, inthe width direction W are preferably greater than the dimension t1 ofthe thickness-direction first outer layer section 6 b 1 in the thicknessdirection T (w1>t1 and w2>t1). With this configuration, the adhesionforce of the ceramic dielectric material in the width-direction firstand second outer layer sections 8 b 1 and 8 b 2 significantly increases,thus effectively significantly reducing or preventing the occurrence ofcracks caused by an internal stress in these sections.

More preferably, both of the dimensions w1 and w2 of the width-directionfirst and second outer layer sections 8 b 1 and 8 b 2, respectively, inthe width direction W are more than about 1.3 times as large as thedimension t1 of the thickness-direction first outer layer section 6 b 1in the thickness direction T (w1/t1>1.3 and w2/t1>1.3), for example.With this configuration, it is possible to more reliably reduce orprevent the occurrence of cracks caused by an internal stress in thewidth-direction first and second outer layer sections 8 b 1 and 8 b 2.

If the dimension T1 of the multilayer unit 10 in the thickness directionT is about 1.15 times or more as large as the dimension W1 of themultilayer unit 10 in the width direction W (T1/W1≧1.15), both of thedimensions w1 and w2 of the width-direction first and second outer layersections 8 b 1 and 8 b 2, respectively, in the width direction W arepreferably more than about 1.5 times as large as the dimension t1 of thethickness-direction first outer layer section 6 b 1 in the thicknessdirection T (w1/t1>1.5 and w2/t1≧1.5). With this configuration, even inthe case of T1/W1≧1.15, it is also possible to more reliably reduce orprevent the occurrence of cracks caused by an internal stress in thewidth-direction first and second outer layer sections 8 b 1 and 8 b 2,and in particular, even under the operating environments in whichthermal shock is repeatedly applied, high reliability is secured.

As shown in FIG. 2, both of dimensions l1 and l2 of the length-directionfirst and second outer layer sections 7 b 1 and 7 b 2, respectively, inthe length direction L are preferably greater than the dimension t1 ofthe thickness-direction first outer layer section 6 b 1 in the thicknessdirection T (l1>t1 and l2>t1). With this configuration, the adhesionforce of the ceramic dielectric material and the adhesion force betweenthe ceramic dielectric material and the conductor material in thelength-direction first and second outer layer sections 7 b 1 and 7 b 2significantly increases, thus effectively reducing or preventing theoccurrence of cracks caused by an internal stress in these sections.

More preferably, both of the dimensions l1 and l2 of thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,respectively, in the length direction L are more than about 1.5 times aslarge as the dimension t1 of the thickness-direction first outer layersection 6 b 1 in the thickness direction T (l1/t1>1.5 and l2/t1>1.5).With this configuration, it is possible to more reliably reduce orprevent the occurrence of cracks caused by an internal stress in thelength-direction first and second outer layer sections 7 b 1 and 7 b 2.

If the dimension T1 of the multilayer unit 10 in the thickness directionT is about 0.67 times or more as large as the dimension L1 of themultilayer unit 10 in the length direction L (T1/L1≧0.67), both of thedimensions l1 and l2 of the length-direction first and second outerlayer sections 7 b 1 and 7 b 2, respectively, in the length direction Lare preferably more than about twice as large as the dimension t1 of thethickness-direction first outer layer section 6 b 1 in the thicknessdirection T (l1/t1>2 and l2/t1>2). With this configuration, even in thecase of T1/L1≧0.67, it is also possible to more reliably reduce orprevent the occurrence of cracks caused by an internal stress in thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,and in particular, even under the operating environments in whichthermal shock is repeatedly applied, high reliability is secured.

In FIGS. 2 and 3, the dimension t1 of the thickness-direction firstouter layer section 6 b 1 in the thickness direction T is preferablyabout 40 μm or smaller, for example. If the dimension t1 is large, thedifference in the coefficients of thermal shrinkage between thethickness-direction inner layer section 6 a including the multilayerunit 10 and the thickness-direction first outer layer section 6 b 1without the multilayer unit 10 becomes more noticeable. This maysignificantly increase a shear stress caused by the difference in thecoefficients of thermal shrinkage, thus increasing the possibility thatcracks will occur at the boundary between the thickness-direction innerlayer section 6 a and the thickness-direction first outer layer section6 b 1. With the dimension t1 having a thickness of about 40 μm orsmaller, for example, the difference in the coefficients of thermalshrinkage is significantly reduced or minimized, thereby effectivelyreducing or preventing the occurrence of cracks at this boundary.

As stated above, the dimension t2 of the thickness-direction secondouter layer section 6 b 2 in the thickness direction T preferably isgreater than the dimension t1 of the thickness-direction first outerlayer section 6 b 1 in the thickness direction T. While considering atradeoff relationship in which by increasing the dimension t2, theoccurrence of cracks due to an external stress is significantly reducedor prevented, but on the other hand, the occurrence of cracks due to aninternal stress is increased, the dimension t2 is reduced to be as smallas possible, thus significantly reducing or preventing the occurrence ofcracks at the boundary between the thickness-direction inner layersection 6 a including the multilayer unit 10 and the thickness-directionsecond outer layer section 6 b 2 without the multilayer unit 10.

In FIG. 3, both of the dimensions w1 and w2 of the width-direction firstand second outer layer sections 8 b 1 and 8 b 2 in the width direction Ware preferably about 52 μm or greater, for example. With thisconfiguration, the adhesion force of the ceramic dielectric material inthe width-direction first and second outer layer sections 8 b 1 and 8 b2 significantly increases, thus effectively significantly reducing orpreventing the occurrence of cracks due to an internal stress in thesesections.

In FIG. 2, both of the dimensions l1 and l2 of the length-directionfirst and second outer layer sections 7 b 1 and 7 b 2 in the lengthdirection L are preferably about 60 μm or greater, for example. Withthis configuration, the adhesion force of the ceramic dielectricmaterial and the adhesion force between the ceramic dielectric materialand the conductor material in the length-direction first and secondouter layer sections 7 b 1 and 7 b 2 significantly increase, thuseffectively reducing or preventing the occurrence of cracks due to aninternal stress in these sections.

In FIG. 3, the dimension W0 of the body 2 in the width direction W, thedimension T1 of the multilayer unit 10 in the thickness direction T, andthe dimension W1 of the multilayer unit 10 in the width direction Wpreferably satisfy the relationship expressed by T1/(W0−W1)≦6.95. Withthis configuration, the adhesion force of the ceramic dielectricmaterial in the width-direction first and second outer layer sections 8b 1 and 8 b 2 is greatly increased, thus effectively reducing orpreventing the occurrence of cracks due to an internal stress in thesesections.

The value expressed by W0-W1 is equal to the total width of thedimension w1 of the width-direction first outer layer section 8 b 1 andthe dimension w2 of the width-direction second outer layer section 8 b 2(that is, W0−W1=w1+w2). The value expressed by T1/(W0−W1) serves as areference, after a step of stacking material sheets (S4) in themanufacturing flow (see FIG. 6) of multilayer ceramic capacitors in thefirst preferred embodiment, for the aspect ratio between the dimensionin the thickness direction T and the dimension in the width direction Wof portions which will define the multilayer units 10 of individualmultilayer ceramic capacitors positioned adjacent to each other in thewidth direction W.

If the above-described relationship expressed by T1/(W0−W1)≦6.95 issatisfied, it indicates that in a step of pressing a set of materialsheets (S5) in the manufacturing flow (see FIG. 6) of multilayer ceramiccapacitors in the first preferred embodiment, a sufficient pressureforce has been applied to portions which will form the width-directionfirst and second outer layer sections 8 b 1 and 8 b 2. As a result, theoccurrence of cracks in the width-direction first and second outer layersections 8 b 1 and 8 b 2 caused by an internal stress are effectivelyreduced or prevented.

In FIG. 2, the dimension L0 of the body 2 in the length direction L, thedimension T1 of the multilayer unit 10 in the thickness direction T, andthe dimension L1 of the multilayer unit 10 in the length direction Lpreferably satisfy the relationship expressed by T1/(L0−L1)≦5.98. Withthis configuration, the adhesion force of the ceramic dielectricmaterial and the adhesion force between the ceramic dielectric materialand the conductor material in the length-direction first and secondouter layer sections 7 b 1 and 7 b 2 are sufficiently increased, thuseffectively reducing or preventing the occurrence of cracks due to aninternal stress in these sections.

The value expressed by L0−L1 is equal to the total length of thedimension l1 of the length-direction first outer layer section 7 b 1 andthe dimension l2 of the length-direction second outer layer section 7 b2 (that is, L0−L1=l1+l2). The value expressed by T1/(L0−L1) serves as areference, after the step of stacking material sheets (S4) in themanufacturing flow (see FIG. 6) of multilayer ceramic capacitors in thefirst preferred embodiment, for the aspect ratio between the dimensionin the thickness direction T and the dimension in the length direction Lof portions which will define multilayer units 10 of individualmultilayer ceramic capacitors positioned adjacent to each other in thelength direction L.

If the above-described relationship expressed by T1/(L0−L1)≦5.98 issatisfied, it indicates that in the step of pressing a set of materialsheets (S5) in the manufacturing flow (see FIG. 6) of multilayer ceramiccapacitors in the first preferred embodiment, a sufficient pressureforce has been applied to portions which will define thelength-direction first and second outer layer sections 7 b 1 and 7 b 2.As a result, the occurrence of cracks in the length-direction first andsecond outer layer sections 7 b 1 and 7 b 2 caused by an internal stressare effectively reduced or prevented.

In FIGS. 2 and 3, the thickness x1 of each of the plurality of innerelectrode layers 4 contained in the multilayer unit 10 is preferablyabout 0.8 times or less as large as the thickness x2 of each of theplurality of ceramic dielectric layers 3 contained in the multilayerunit 10 (x1/x2≦0.8), for example.

With this configuration, after the step of stacking material sheets (S4)in the manufacturing flow (see FIG. 6) of multilayer ceramic capacitorsin the first preferred embodiment, the difference between the totalthickness of ceramic bases 12 and conductor patterns 13 which willdefine the multilayer unit 10 and the total thickness of ceramic bases12 which will define the length-direction first and second outer layersections 7 b 1 and 7 b 2 and the width-direction first and second outerlayer sections 8 b 1 and 8 b 2 and conductor patterns 13 which willdefine the length-direction first and second outer layer sections 7 b 1and 7 b 2 is reduced (see FIGS. 8A through 9B).

Thus, in the step of fixing a set of material sheets with pressure (S5)in the manufacturing flow (see FIG. 6), a sufficient pressure force isapplied to portions which will define the length-direction first andsecond outer layer sections 7 b 1 and 7 b 2 and the width-directionfirst and second outer layer sections 8 b 1 and 8 b 2. As a result, theoccurrence of cracks in these portions caused by an internal stress iseffectively significantly reduced or prevented.

In FIGS. 2 and 3, each of the dimensions l1 and l2 of thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,respectively, in the length direction L is preferably greater than thedimensions w1 and w2 of the width-direction first and second outer layersections 8 b 1 and 8 b 2, respectively, in the width direction W (l1>w1,l1>w2, l2>w1, l2>w2).

As stated above, the length-direction first and second outer layersections 7 b 1 and 7 b 2 are respectively constituted by ceramicdielectric layers 3 and the inner electrode layers 4 which will definethe first and second extension portions 4 c 1 and 4 c 2. On the otherhand, the width-direction first and second outer layer sections 8 b 1and 8 b 2 are constituted only by ceramic dielectric layers 3 and do notinclude any inner electrode layer 4. Thus, interlayer delamination islikely to occur in the boundary between the first and second extensionportions 4 c 1 and 4 c 2 and adjacent ceramic dielectric layers 3 in thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,as discussed above.

Concerning this point, from the viewpoint of significantly reducing orpreventing the occurrence of interlayer delamination in thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,it is preferable that each of the dimensions l1 and l2 of thelength-direction first and second outer layer sections 7 b 1 and 7 b 2be greater than the dimensions w1 and w2 of the width-direction firstand second outer layer sections 8 b 1 and 8 b 2, which are set so thatthe occurrence of cracks in the width-direction first and second outerlayer sections 8 b 1 and 8 b 2 is significantly reduced or prevented.

With the above-described configuration, not only the occurrence ofcracks in the length-direction first and second outer layer sections 7 b1 and 7 b 2 and the width-direction first and second outer layersections 8 b 1 and 8 b 2 caused by an internal stress can besignificantly reduced or prevented, but also the occurrence ofinterlayer delamination in the length-direction first and second outerlayer sections 7 b 1 and 7 b 2 caused by an internal stress can besignificantly reduced or prevented.

More preferably, each of the dimensions l1 and l2 of thelength-direction first and second outer layer sections 7 b 1 and 7 b 2in the length direction L is more than about 1.15 times as large as thedimensions w1 and w2 of the width-direction first and second outer layersections 8 b 1 and 8 b 2 in the width direction W (l1/w1>1.15,l1/w2>1.15, l2/w1>1.15, l2/w2>1.15), for example. With thisconfiguration, it is possible to more reliably reduce or prevent theoccurrence of interlayer delamination in the length-direction first andsecond outer layer sections 7 b 1 and 7 b 2 caused by an internalstress.

FIG. 6 is a flowchart illustrating a non-limiting example of amanufacturing flow for the multilayer ceramic capacitor 1A shown inFIG. 1. The manufacturing flow for the multilayer ceramic capacitor 1Awill be discussed below with reference to FIG. 6. In this manufacturingflow, a plurality of multilayer ceramic capacitors 1A are mass-producedtogether in the following manner. A material which will form a pluralityof multilayer ceramic capacitors 1A is processed together until ahalfway point through a manufacturing process so as to fabricate amother block. Then, the mother block is divided into individual chips,and the individual chips are then processed.

The manufacturing process will be discussed below more specifically. Instep S1, ceramic slurry is prepared first. More specifically, a ceramicpowder, a binder, and a solvent are mixed at a predetermined mixingratio so as to form ceramic slurry.

Then, in step S2, ceramic green sheets are formed. More specifically,the ceramic slurry is formed into a sheet-shaped shape on a carrier filmby using a die coater, a gravure coater, or a micro gravure coater,thereby forming ceramic green sheets.

Then, in step S3, material sheets are formed. More specifically, aconductor paste is printed on each ceramic green sheet by using screenprinting or gravure printing such that a predetermined conductor patternis formed on the ceramic green sheet. As a result, a material sheethaving a predetermined conductor pattern on a ceramic green sheet isformed.

Material sheets formed in step S3 will be discussed below in details.FIG. 7 is an exploded perspective view illustrating the multilayerstructure of a set of base sheets 11, which will form the body 2 of themultilayer ceramic capacitor 1A shown in FIG. 1.

As shown in FIG. 7, the body 2 is fabricated by using the set of basesheets 11 constituted by a plurality of base sheets 11A, 11B1, and 11B2which are configured differently. More specifically, the body 2 isfabricated by stacking the plurality of base sheets 11A, 11B1, and 11B2in a predetermined order and by then fixing them with pressure andfiring them.

The base sheet 11A is constituted only by a ceramic base 12 on which noconductor pattern is formed. The base sheet 11A will be used as aceramic dielectric layer 3 which forms the thickness-direction first orsecond outer layer section 6 b 1 or 6 b 2 after the body 2 is fired.

The base sheets 11B1 and 11B2 are each constituted by a ceramic base 12on which a conductor pattern 13 having a predetermined shape is formed.The conductor patterns 13 of the base sheets 11B1 and 11B2 will be usedas inner electrode layers 4 after the body 2 is fired. The ceramic bases12 of the base sheets 11B1 and 11B2 will be used as ceramic dielectriclayers 3, most of which will form the thickness-direction inner layersection 6 a.

The layout of a material sheet formed in step S3 is as follows. By usingthe base sheet 11B1 or 11B2 shown in FIG. 7 as a unit, a plurality ofbase sheets having the same shape as that of the base sheet 11B1 or 11B2which is determined as a unit are two-dimensionally arranged in amatrix.

Since the base sheets 11B1 and 11B2 preferably have the same shape,sheets having the same conductor pattern may be used as material sheetsincluding the base sheets 11B1 and those including the base sheets 11B2.In a step of stacking a set of material sheets, which will be discussedbelow, material sheets having the same conductor pattern are displacedfrom each other by half pitch, thereby obtaining the multilayerstructure of the base sheets 11B1 and 11B2 shown in FIG. 7.

As material sheets, not only material sheets having the above-describedconductor patterns, but also ceramic green sheets which are formedwithout being subjected to step S3 are also prepared.

Then, referring back to FIG. 6, in step S4, the material sheets arestacked. More specifically, by stacking the plurality of material sheetsaccording to a predetermined rule, the above-described units (basesheets 11B1 and 11B2) are disposed within the stacked material sheets inthe stacking direction so as to obtain the multilayer structure shown inFIG. 7.

Then, in step S5, the set of stacked material sheets is fixed withpressure. More specifically, pressure is applied to the set of materialsheets in the stacking direction by using, for example, isostaticpressing, thereby fixing the set of material sheets.

FIGS. 8A through 9B are schematic sectional views illustrating a step offixing a set of material sheets 20 with pressure in step S5 of FIG. 6.FIGS. 8A and 8B are sectional views along the length direction L of themultilayer ceramic capacitor 1A to be manufactured, and FIGS. 9A and 9Bare sectional views along the width direction W thereof. FIGS. 8A and 9Aillustrate the state of the set of material sheets 20 which have not yetbeen fixed with pressure, while FIGS. 8B and 9B illustrate the state ofthe set of material sheets 20 which have been fixed with pressure.

As shown in FIGS. 8A through 9B, in step S5, the set of material sheets20 which are stacked according to the predetermined rule are sandwichedbetween a pair of pressure plates 50 in the stacking direction, andisostatic pressure is applied to the pressure plates 50, thereby fixingthe set of material sheets 20.

As shown in FIG. 8A, regions X in which many conductor patterns 13 aredisposed and regions Y in which a relatively small number of conductorpatterns 13 are disposed are alternately arranged in the lengthdirection L of the set of material sheets 20. The region X will form thelength-direction inner layer section 7 a of the multilayer ceramiccapacitor 1A, while the region Y will form the length-direction first orsecond outer layer section 7 b 1 or 7 b 2 of the multilayer ceramiccapacitor 1A.

As shown in FIG. 9A, regions X in which many conductor patterns 13 aredisposed and regions Z in which no conductor pattern 13 is disposed arealternately arranged in the width direction W of the set of materialsheets 20. The region X will form the width-direction inner layersection 8 a of the multilayer ceramic capacitor 1A, while the region Zwill form the width-direction first or second outer layer section 8 b 1or 8 b 2 of the multilayer ceramic capacitor 1A.

A sheet-shaped elastic member 60 is interposed between each of thepressure plates 50 and the set of material sheets 20. The sheet-shapedelastic members 60 are used to adjust a pressure force to be applied tothe individual regions of the set of material sheets 20 through the pairof pressure plates 50. The sheet-shaped elastic members 60 are made of aresin, for example, rubber.

Since the ceramic bases 12 are made of a ceramic dielectric material,they are relatively soft and are easy to press. In contrast, since theconductor patterns 13 are made of a conductor material, they arerelatively hard and are difficult to press. In the regions X, manyconductor patterns 13 are densely disposed, and on the other hand, inthe regions Y, a smaller number of conductor patterns 13 are disposedthan in the regions X, and in the regions Z, no conductor pattern 13 isdisposed. Accordingly, the regions X are relatively difficult to press,while the regions Y and Z are relatively easy to press.

Thus, as discussed above, a sheet-shaped elastic member 60 is interposedbetween each of the pressure plates 50 and the set of material sheets20. The set of material sheets 20 are fixed with pressure by using thepressure plates 50 via the sheet-shaped elastic members 60, and then,the sheet-shaped elastic members 60 are elastically deformed so as toadjust the pressure force to be applied to the individual regions of theset of material sheets 20.

As discussed above, from the viewpoint of reducing or preventing theoccurrence of cracks caused by an internal stress, it is important thatthe set of material sheets 20 in the regions Y and Z be pressed with asufficient pressure force in step S5, and in order to implement this,certain ones of the above-described conditions preferably are satisfied.

By pressing the set of material sheets 20 as described above, a motherblock 30 shown in FIGS. 8B and 9B is fabricated.

Then, in step S6, the mother block 30 is divided. More specifically, themother block 30 is divided in a matrix form by push-cutting or dicing,thereby cutting out the above-described individual chips. Each of thechips cut out from the mother block 30 has a multilayer structure, suchas that shown in FIG. 7.

Then, in step S7, the chips are fired. More specifically, the chips areheated to a predetermined temperature, thereby performing sintering onthe ceramic dielectric material and the conductor material.

Then, in step S8, the chips are barrel-polished. More specifically, thechips subjected to firing are sealed within a small box called a barrel,together with media balls having a higher hardness than the ceramicdielectric material. Then, by rotating the barrel, the chips can bepolished. By performing this barrel-polishing, the outer surfaces (inparticular, corners) of the chips are curved and rounded. As a result,the above-described body 2 is formed.

Then, in step S9, outer electrodes are formed. More specifically, aconductor paste is applied to end portions including the first andsecond end surfaces 2 b 1 and 2 b 2 of the body 2 so as to form a metalfilm, and then, sintering processing is performed on the metal film.Then, the metal film is sequentially Ni-plated and Sn-plated. As aresult, the first and second outer electrodes 5 a and 5 b are formed onthe outer surfaces of the body 2.

After the above-described series of steps, the multilayer ceramiccapacitor 1A configured as shown in FIGS. 1 through 5 is manufactured.

In the multilayer ceramic capacitor 1A of the first preferredembodiment, among the above-described conditions, at least the conditionthat both of the dimensions w1 and w2 of the width-direction first andsecond outer layer sections 8 b 1 and 8 b 2, respectively, in the widthdirection W are greater than the dimension t1 of the thickness-directionfirst outer layer section 6 b 1 in the thickness direction T issatisfied (w1>t1 and w2>t1).

By forming the multilayer ceramic capacitor 1A of the first preferredembodiment in this manner, as stated above, the adhesion force of theceramic dielectric material in the width-direction first and secondouter layer sections 8 b 1 and 8 b 2 is sufficiently increased, thuseffectively reducing or preventing the occurrence of cracks caused by aninternal stress in these sections. As a result, it is possible toimprove the reliability of multilayer ceramic capacitors as products andthe yield in a manufacturing process.

FIG. 10 is a sectional view illustrating a multilayer ceramic capacitormount body 100 of the first preferred embodiment. The multilayer ceramiccapacitor mount body 100 will be described below with reference to FIG.10.

As shown in FIG. 10, the multilayer ceramic capacitor mount body 100 ofthe first preferred embodiment includes the above-described multilayerceramic capacitor 1A and a wiring board 101, which defines and serves asa mounting member on which the multilayer ceramic capacitor 1A ismounted. The multilayer ceramic capacitor 1A is mounted on the wiringboard 101 such that its second principal surface 2 a 2 faces the wiringboard 101. As the mounting board, a member other than the wiring board101 may be used.

The configuration of the multilayer ceramic capacitor mount body 100will be discussed more specifically. A pair of lands 102 is disposed onthe surface of the wiring board 101 such that the lands 102 are spacedapart from each other. The first and second outer electrodes 5 a and 5 bof the multilayer ceramic capacitor 1A are disposed on the lands 102such that the first outer electrode 5 a faces one land 102 and thesecond outer electrode 5 b faces the other land 102. Solder 103, whichis a bonding medium, is disposed each of between the first outerelectrode 5 a and one land 102 and between the second outer electrode 5b and the other land 102, thus bonding the first and second outerelectrodes 5 a and 5 b to the respective lands 102. As the bondingmedium, a medium other than the solder 103 may be used.

A dimension WL of the pair of lands 102 in the width direction W ispreferably smaller than the dimension W0 of the body 2 in the widthdirection W. With this configuration, the first and second outerelectrodes 5 a and 5 b are subjected to a compressive stress appliedfrom the solder 103 along the width direction W when the solder 103 issolidified. This compressive stress also acts on a boundary portionbetween the multilayer unit 10 and the thickness-direction second outerlayer section 6 b 2. Accordingly, with the above-describedconfiguration, the stress acting on this boundary portion is relaxed,thus significantly reducing or preventing the occurrence of cracks inthis boundary portion.

Additionally, the dimension WL of the pair of lands 102 in the widthdirection W is preferably smaller than the dimension W1 of themultilayer unit 10 in the width direction W. With this configuration,when the solder 103 is solidified, the compressive stress acting on theboundary portion between the multilayer unit 10 and thethickness-direction second outer layer section 6 b 2 is furtherenhanced. This further relaxes the stress acting on this boundaryportion, thus significantly reducing or preventing the occurrence ofcracks in this boundary portion more reliably.

FIG. 11 is a plan view illustrating a multilayer ceramic capacitor array200 of the first preferred embodiment. FIG. 12 is a schematic sectionalview taken along line XII-XII of FIG. 11. The multilayer ceramiccapacitor array 200 of the first preferred embodiment will be describedbelow with reference to FIGS. 11 and 12.

As shown in FIGS. 11 and 12, the multilayer ceramic capacitor array 200of the first preferred embodiment includes a plurality of multilayerceramic capacitors 1A discussed above and a package 201 to package theplurality of multilayer ceramic capacitors 1A together therein. Thepackage 201 includes an elongated carrier tape 202 and a cover tape 203.The carrier tape 202 includes a plurality of recessed portions 202 adisposed apart from each other and storing the plurality of multilayerceramic capacitors 1A therein. The cover tape 203 is attached to thecarrier tape 202 such that it covers the plurality of recessed portions202 a. The plurality of multilayer ceramic capacitors 1A are stored inthe respective recessed portions 202 a such that their second principalsurfaces 2 a 2 face bottom portions 202 b of the respective recessedportions 202 a.

The plurality of multilayer ceramic capacitors 1A contained in themultilayer ceramic capacitor array 200 are extracted from the package201 one by one and are mounted on the above-described wiring board 101.More specifically, in the state in which the cover tape 203 is removedfrom the carrier tape 202, the multilayer ceramic capacitors 1A aresucked and held at the side from their first principal surfaces 2 a 1 bya suction head, such as a chip mounter, so as to be removed from thecarrier tape 202 and mounted on the wiring board 101.

As stated above, the multilayer ceramic capacitors 1A are stored in therespective recessed portions 202 a such that their second principalsurfaces 2 a 2 face the bottom portions 202 b of the respective recessedportions 202 a. With this arrangement, a mounting operation using asuction head, such as a chip mounter, can be performed smoothly. Thus,by forming the multilayer ceramic capacitor array 200 of the firstpreferred embodiment as described above, it is possible to easilymanufacture the above-described multilayer ceramic capacitor mount body100 of the first preferred embodiment.

Second Preferred Embodiment

FIG. 13 is a schematic perspective view illustrating a multilayerceramic capacitor 1B according to a second preferred embodiment of thepresent invention. FIGS. 14 and 15 are schematic sectional views takenalong lines XIV-XIV and XV-XV, respectively, of FIG. 13. Theconfiguration of the multilayer ceramic capacitor 1B of the secondpreferred embodiment will be described below with reference to FIGS. 13through 15.

As shown in FIGS. 13 through 15, the multilayer ceramic capacitor 1B ofthe second preferred embodiment is different from the multilayer ceramiccapacitor 1A of the first preferred embodiment in the configuration ofthe thickness-direction second outer layer section 6 b 2, for example.More specifically, the thickness-direction second outer layer section 6b 2 of the multilayer ceramic capacitor 1B includes an inner portion 6 b21 disposed adjacent to the thickness-direction inner layer section 6 aand an outer portion 6 b 22 which is disposed adjacent to the innerportion 6 b 21 and which defines the second principal surface 2 a 2.

The inner portion 6 b 21 is constituted by a ceramic dielectric layer 3made of a ceramic dielectric material, which preferably is the same type(that is, having the same composition) as that of thethickness-direction inner layer section 6 a and the thickness-directionfirst outer layer section 6 b 1. The outer portion 6 b 22 is constitutedby a ceramic dielectric layer 9 made of a ceramic dielectric material,which is a different type (that is, having a different composition) fromthat of the thickness-direction inner layer section 6 a and thethickness-direction first outer layer section 6 b 1.

The ceramic dielectric layers 3 defining the thickness-direction innerlayer section 6 a, the thickness-direction first outer layer section 6 b1, and the inner portion 6 b 21 and the ceramic dielectric layer 9defining the outer portion 6 b 22 contain a perovskite compoundexpressed by ABO₃ (“A” contains Ba and “B” contains Ti) as a principalcomponent. A typical example of a perovskite compound expressed by ABO₃is barium titanate (BaTiO₃).

The ceramic dielectric layers 3 defining the thickness-direction innerlayer section 6 a, the thickness-direction first outer layer section 6 b1, and the inner portion 6 b 21 and the ceramic dielectric layer 9defining the outer portion 6 b 22 contain Si as a secondary component.Si is contained in the ceramic dielectric layers 3 and 9 by adding a Sicompound, such as glass or SiO₂, to a perovskite compound expressed byABO₃. Another compound, such as a Mn compound, an Mg compound, a Cocompound, a Ni compound, or a rare earth compound, may be added to aperovskite compound expressed by ABO₃.

The composition ratio of Si to Ti contained in the ceramic dielectriclayer 9 defining the outer portion 6 b 22 is higher than that in theceramic dielectric layers 3 defining the thickness-direction inner layersection 6 a, the thickness-direction first outer layer section 6 b 1,and the inner portion 6 b 21. The composition ratio is typicallyrepresented by a molar ratio. The molar ratio of Si to Ti contained inthe ceramic dielectric layer 3 and that in the ceramic dielectric layer9 may be measured by using a wavelength-dispersive X-ray spectrometer(WDX), for example.

The molar ratio of Si to Ti contained in the ceramic dielectric layer 9defining the outer portion 6 b 22 is preferably about 0.013 to about0.030, for example. If the molar ratio of Si to Ti contained in theceramic dielectric layer 9 is lower than about 0.013 or higher thanabout 0.030, the reliability of the outer portion 6 b 22 may bedecreased.

The molar ratio of Si to Ti contained in the ceramic dielectric layer 9defining the outer portion 6 b 22 is preferably higher than that in theceramic dielectric layer 3 defining the inner portion 6 b 21 by about0.004 or higher, and more preferably by about 0.008 or higher, forexample.

A boundary portion P1 of the outer portion 6 b 22 with the inner portion6 b 21 has a larger Si content than the thickness-direction centralportion of the outer portion 6 b 22. A surface layer portion P2 of theouter portion 6 b 22 close to the second principal surface 2 a 2 alsohas a higher Si content than the thickness-direction central portion ofthe outer portion 6 b 22. A determination as to whether or not theboundary portion P1 and the surface layer portion P2 of the outerportion 6 b 22 have a high Si content ratio may be made by elementmapping created by using a field emission wavelength-dispersive X-rayspectrometer (FE-WDX), for example.

In the multilayer ceramic capacitor 1B of the second preferredembodiment, as well as in the multilayer ceramic capacitor 1A of thefirst preferred embodiment, among the above-described conditionsdiscussed in the first preferred embodiment, at least the condition thatboth of the dimensions w1 and w2 of the width-direction first and secondouter layer sections 8 b 1 and 8 b 2, respectively, in the widthdirection W are greater than the dimension t1 of the thickness-directionfirst outer layer section 6 b 1 in the thickness direction T issatisfied (w1>t1 and w2>t1). Thus, advantages similar to those discussedin the first preferred embodiment can also be obtained.

Additionally, of the second preferred embodiment, as stated above, themolar ratio of Si to Ti contained in the ceramic dielectric layer 9defining the outer portion 6 b 22 is higher than that in the ceramicdielectric layers 3 defining the thickness-direction inner layer section6 a, the thickness-direction first outer layer section 6 b 1, and theinner portion 6 b 21. That is, the outer portion 6 b 22 contains agreater amount of Si than the inner portion 6 b 21. The coefficient ofthermal shrinkage of a ceramic dielectric layer having a higher Sicontent ratio is greater than that of a ceramic dielectric layer havinga lower Si content ratio. Accordingly, the coefficient of thermalshrinkage of the outer portion 6 b 22 is greater than that of the innerportion 6 b 21. Thus, the coefficient of thermal shrinkage of the outerportion 6 b 22 is closer to that of the inner electrode layers 4included in the thickness-direction inner layer section 6 a.

Thus, in the multilayer ceramic capacitor 1B, it is possible to relax aninternal stress which is caused by the difference in the coefficients ofthermal shrinkage between the ceramic dielectric layers 3 and the innerelectrode layers 4 and which acts on the boundary portion between thethickness-direction inner layer section 6 a and the thickness-directionsecond outer layer section 6 b 2, thus effectively reducing orpreventing the occurrence of cracks in this boundary portion.

If the molar ratio of Si to Ti contained in the ceramic dielectric layer9 defining the outer portion 6 b 22 is higher than that in the ceramicdielectric layer 3 defining the inner portion 6 b 21 by about 0.004 orhigher, the occurrence of cracks in this boundary portion is reduced orprevented more effectively. If the above-described molar ratio is higherby about 0.008 or higher, the occurrence of cracks in this boundaryportion is reduced or prevented even more effectively.

In the multilayer ceramic capacitor 1B of the second preferredembodiment, if certain ones of the following conditions are satisfied,the occurrence of cracks caused by an internal stress are effectivelyreduced or prevented, thus improving the reliability of multilayerceramic capacitors as products and the yield in a manufacturing process.These conditions have been established on the basis of evaluationresults of first through fourth verification tests, which will bediscussed later.

As shown in FIG. 15, both of dimensions w1 and w2 of the width-directionfirst and second outer layer sections 8 b 1 and 8 b 2, respectively, inthe width direction W are preferably greater than a dimension t21 of theinner portion 6 b 21 of the thickness-direction second outer layersection 6 b 2 in the thickness direction T (w1>t21 and w2>t21). Withthis configuration, the adhesion force of the ceramic dielectricmaterial in the width-direction first and second outer layer sections 8b 1 and 8 b 2 significantly increases, thus effectively reducing orpreventing the occurrence of cracks caused by an internal stress inthese sections.

More preferably, both of the dimensions w1 and w2 of the width-directionfirst and second outer layer sections 8 b 1 and 8 b 2, respectively, inthe width direction W are more than about 1.3 times as large as thedimension t21 of the inner portion 6 b 21 of the thickness-directionsecond outer layer section 6 b 2 in the thickness direction T(w1/t21>1.3 and w2/t21>1.3), for example. With this configuration, it ispossible to more reliably reduce or prevent the occurrence of crackscaused by an internal stress in the width-direction first and secondouter layer sections 8 b 1 and 8 b 2.

If the dimension T1 of the multilayer unit 10 in the thickness directionT preferably is about 1.15 times or more as large as the dimension W1 ofthe multilayer unit 10 in the width direction W (T1/W11.15), both of thedimensions w1 and w2 of the width-direction first and second outer layersections 8 b 1 and 8 b 2, respectively, in the width direction W arepreferably more than about 1.5 times as large as the dimension t21 ofthe inner portion 6 b 21 of the thickness-direction second outer layersection 6 b 2 in the thickness direction T (w1/t21>1.5 and w2/t21>1.5).With this configuration, even in the case of T1/W1≧1.15, it is alsopossible to more reliably reduce or prevent the occurrence of crackscaused by an internal stress in the width-direction first and secondouter layer sections 8 b 1 and 8 b 2, and in particular, even under theoperating environments in which thermal shock is repeatedly applied,high reliability is secured.

As shown in FIG. 14, both of dimensions l1 and l2 of thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,respectively, in the length direction L are preferably greater than thedimension t21 of the inner portion 6 b 21 of the thickness-directionsecond outer layer section 6 b 2 in the thickness direction T (l1>t21and l2>t21). With this configuration, the adhesion force of the ceramicdielectric material and the adhesion force between the ceramicdielectric material and the conductor material in the length-directionfirst and second outer layer sections 7 b 1 and 7 b 2 significantlyincrease, thus effectively reducing or preventing the occurrence ofcracks caused by an internal stress in these sections.

More preferably, both of the dimensions l1 and l2 of thelength-direction first and second outer layer sections 7 b 1 and 7 b 2,respectively, in the length direction L are more than about 1.5 times aslarge as the dimension t21 of the inner portion 6 b 21 of thethickness-direction second outer layer section 6 b 2 in the thicknessdirection T (l1/t21>1.5 and l2/t21>1.5), for example. With thisconfiguration, it is possible to more reliably reduce or prevent theoccurrence of cracks caused by an internal stress in thelength-direction first and second outer layer sections 7 b 1 and 7 b 2.

If the dimension T1 of the multilayer unit 10 in the thickness directionT is about 0.67 times or more as large as the dimension L1 of themultilayer unit 10 in the length direction L (T1/L1≧0.67), both of thedimensions l1 and l2 of the length-direction first and second outerlayer sections 7 b 1 and 7 b 2, respectively, in the length direction Lare preferably more than twice as large as the dimension t21 of theinner portion 6 b 21 of the thickness-direction second outer layersection 6 b 2 in the thickness direction T (l1/t21>2 and l2/t21>2). Withthis configuration, even in the case of T1/L1≧0.67, it is also possibleto more reliably reduce or prevent the occurrence of cracks caused by aninternal stress in the length-direction first and second outer layersections 7 b 1 and 7 b 2, and in particular, even under the operatingenvironments in which thermal shock is repeatedly applied, highreliability is secured.

As shown in FIGS. 14 and 15, the dimension t22 of the outer portion 6 b22 of the thickness-direction second outer layer section 6 b 2 in thethickness direction T is preferably equal to or greater than thedimension t21 of the inner portion 6 b 21 of the thickness-directionsecond outer layer section 6 b 2 in the thickness direction T. With thisconfiguration, the above-described stress relaxing effect exhibited bythe thermal shrinkage of the outer portion 6 b 22 is more likely to beproduced at the boundary portion between the thickness-direction innerlayer section 6 a and the thickness-direction second outer layer section6 b 2, thus effectively reducing or preventing the occurrence of cracksat this boundary portion.

In FIGS. 14 and 15, the dimension t21 of the inner portion 6 b 21 of thethickness-direction second outer layer section 6 b 2 in the thicknessdirection T is preferably about 20 μm or greater, for example. With thisconfiguration, the diffusion of Si contained in the outer portion 6 b 22into the thickness-direction inner layer section 6 a is reduced orprevented. If the Si content ratio in the thickness-direction innerlayer section 6 a is too high, the grain growth of ceramic particles inthe ceramic dielectric layers 3 included in the thickness-directioninner layer section 6 a accelerates excessively in a step of firing thebody 2, thus reducing the withstand voltage characteristics of theceramic dielectric layers 3. As a result, the thickness-direction innerlayer section 6 a is more likely to be short-circuited. However, withthe above-described configuration, it is possible to significantlyreduce or prevent the occurrence of the short-circuiting of thethickness-direction inner layer section 6 a by maintaining the withstandvoltage characteristics of the ceramic dielectric layers 3 included inthe thickness-direction inner layer section 6 a.

The dimension t21 of the inner portion 6 b 21 of the thickness-directionsecond outer layer section 6 b 2 in the thickness direction T preferablyis smaller than the dimension t1 of the thickness-direction first outerlayer section 6 b 1 in the thickness direction T, for example. Even withthis configuration, because of the provision of the outer portion 6 b 22outside the inner portion 6 b 21, the entry of moisture into thethickness-direction inner layer section 6 a from the inner portion 6 b21 and the outer portion 6 b 22 is significantly reduced or prevented.Thus, even if the dimension t21 of the inner portion 6 b 21 of thethickness-direction second outer layer section 6 b 2 is reduced to besufficiently small, the reliability is not decreased.

In FIGS. 14 and 15, the dimension t22 of the outer portion 6 b 22 of thethickness-direction second outer layer section 6 b 2 in the thicknessdirection T is preferably about 30 μm or greater, for example. With thisconfiguration, the above-described stress relaxing effect exhibited bythe thermal shrinkage of the outer portion 6 b 22 is produced at theboundary portion between the thickness-direction inner layer section 6 aand the thickness-direction second outer layer section 6 b 2, thuseffectively significantly reducing or preventing the occurrence ofcracks at this boundary portion.

As discussed above, in the multilayer ceramic capacitor 1B of the secondpreferred embodiment, the Si content ratio in the boundary portion P1 ofthe outer portion 6 b 22 with the inner portion 6 b 21 and that in thesurface layer portion P2 of the outer portion 6 b 22 close to the secondprincipal surface 2 a 2 are preferably set to be higher than that in thethickness-direction central portion of the outer portion 6 b 22. Thisconfiguration is implemented preferably by setting a temperature and agaseous atmosphere at which Si segregates from grain boundaries ofceramic particles in the step of firing the body 2.

More specifically, in the step of firing the body 2, by setting atemperature and a gaseous atmosphere at which Si segregates from grainboundaries of ceramic particles, in the outer portion 6 b 22 containinga greater amount of Si, the grain growth of ceramic particles isencouraged, and Si segregates from the grain boundaries of coarsenedceramic particles. Segregated Si moves along the grain boundaries of theceramic particles and concentrates toward the boundary portion P1 andthe surface layer portion P2. As a result, the Si content ratio in theboundary portion P1 and that in the surface layer portion P2 of theouter portion 6 b 22 become higher than that in the thickness-directioncentral portion of the outer portion 6 b 22.

The Si content ratio in the boundary portion P1 of the outer portion 6 b22 with the inner portion 6 b 21 is preferably higher than that in thethickness-direction central portion of the outer portion 6 b 22, thusimproving the adhesion force between the outer portion 6 b 22 and theinner portion 6 b 21. The reason for this may be as follows. Si whichhas moved along the grain boundaries of the ceramic particles asdescribed above fills many small gaps at the interface between the outerportion 6 b 22 and the inner portion 6 b 21, thus coupling the outerportion 6 b 22 and the inner portion 6 b 21 to each other. Accordingly,if the formation of the inner portion 6 b 21 and the formation of theouter portion 6 b 22 are separately performed, small gaps may be createdat the interface between the inner portion 6 b 21 and the outer portion6 b 22, and the concentration of segregated Si in the boundary portionP1 may be encouraged, thus enhancing the adhesion force between theouter portion 6 b 22 and the inner portion 6 b 21.

The Si content ratio in the surface layer portion P2 of the outerportion 6 b 22 close to the second principal surface 2 a 2 is preferablyhigher than that in the thickness-direction central portion of the outerportion 6 b 22, thus reducing or preventing a decrease in the mechanicalstrength of the body 2 when forming the first and second outerelectrodes 5 a and 5 b. In the formation of the first and second outerelectrodes 5 a and 5 b, if glass components contained in the first andsecond outer electrodes 5 a and 5 b react with the ceramic dielectricmaterial of the body 2, the mechanical strength of the body 2 isdecreased. However, if the Si content ratio in the outer portion 6 b 22is high, the reaction of glass components contained in the first andsecond outer electrodes 5 a and 5 b with the ceramic dielectric materialof the body 2 is significantly reduced or prevented.

In each of the ceramic dielectric layers 3 and 9, if a rare earthcompound is contained in a perovskite compound expressed by ABO₃, whichis a principal component, the molar ratio of a rare earth element to Tiin the ceramic dielectric layers 3 defining the thickness-directioninner layer section 6 a, the thickness-direction first outer layersection 6 b 1, and the inner portion 6 b 21 is preferably higher thanthat in the ceramic dielectric layer 9 defining the outer portion 6 b22. That is, the thickness-direction inner layer section 6 a, thethickness-direction first outer layer section 6 b 1, and the innerportion 6 b 21 preferably contain a greater amount of rare earth elementthan the outer portion 6 b 22.

As a rare earth element, Dy, Gd, Y, or La may be added to improve thefunctions of the multilayer ceramic capacitor 1B. More specifically, byadding a rare earth element, it is possible to stabilize the capacitortemperature characteristics and to prolong the life of the multilayerceramic capacitor 1B by maintaining the insulation resistance (IR) valueeven under a high-temperature load.

A rare earth element is likely to concentrate in a grain boundary ofceramic particles or a segregation layer and also to elute towater-soluble flux. Accordingly, when mounting the multilayer ceramiccapacitor 1B, ceramic components containing a rare earth element mayelute to an organic acid, such as adipic acid, contained inwater-soluble flux used for soldering. In this case, cracks may occur inan outer layer section of the body 2 which is embrittled as a result ofthe eluting of ceramic components.

Accordingly, the molar ratio of a rare earth element to Ti in theceramic dielectric layers 3 defining the thickness-direction inner layersection 6 a, the thickness-direction first outer layer section 6 b 1,and the inner portion 6 b 21 is preferably about 0.003 or higher, andthe molar ratio of a rare earth element to Ti in the ceramic dielectriclayer 9 defining the outer portion 6 b 22 is preferably lower than about0.003, for example. With this configuration, it is possible to stabilizethe capacitor temperature characteristics and to prolong the life of themultilayer ceramic capacitor 1B by maintaining the insulation resistance(IR) value even under a high-temperature load, and also to significantlyreduce or prevent the occurrence of cracks in the outer portion 6 b 22,which would be caused by the embrittlement of the outer portion 6 b 22as a result of the eluting of ceramic components from the outer portion6 b 22.

Although a detailed explanation is omitted, it has been validated, as aresult of conducting verification tests (different from first throughthird verification tests, which will be discussed later) by changing thecontent of Dy used as a rare earth element, that the above-describedadvantages were obtained due to the above-described characteristicpoints. It has also been validated that the advantages were alsoobtained when Gd, Y, or La was used instead of Dy, for example.

In each of the ceramic dielectric layers 3 and 9, if a Mn compound iscontained in a perovskite compound expressed by ABO₃, which is aprincipal component, the molar ratio of a Mn compound to Ti in theceramic dielectric layers 3 defining the thickness-direction inner layersection 6 a, the thickness-direction first outer layer section 6 b 1,and the inner portion 6 b 21 is preferably higher than that in theceramic dielectric layer 9 defining the outer portion 6 b 22. That is,the thickness-direction inner layer section 6 a, the thickness-directionfirst outer layer section 6 b 1, and the inner portion 6 b 21 preferablycontain a greater amount of Mn than the outer portion 6 b 22.

The color of a ceramic dielectric layer containing a smaller amount ofMn is lighter than that containing a greater amount of Mn. With thisconfiguration, the color of the outer portion 6 b 22 is made brighterthan that of the thickness-direction inner layer section 6 a, thethickness-direction first outer layer section 6 b 1, and the innerportion 6 b 21. It is thus easy to visually distinguish the first andsecond principal surfaces 2 a 1 and 2 a 2 of the multilayer ceramiccapacitor 1B from each other.

Accordingly, by performing image processing by capturing an image of themultilayer ceramic capacitor 1B with an imaging camera, the orientationof the multilayer ceramic capacitor 1B in the thickness direction T iscapable of being identified. Thus, when mounting the multilayer ceramiccapacitor 1B, the orientation of the multilayer ceramic capacitor 1B iscapable of being automatically identified so that the second principalsurface 2 a 2 will face a mounting member, such as the wiring board 101.

For example, the molar ratio of Mn to Ti in the ceramic dielectriclayers 3 defining the thickness-direction inner layer section 6 a, thethickness-direction first outer layer section 6 b 1, and the innerportion 6 b 21 is preferably about 0.0008 or higher, and the molar ratioof Mn to Ti in the ceramic dielectric layer 9 defining the outer portion6 b 22 is preferably lower than about 0.0008, for example.

Although a detailed explanation is omitted, it has been validated, as aresult of conducting verification tests (different from first throughthird verification tests, which will be discussed later) by changing thecontent of Mn, that the above-described advantages were obtained due tothe above-described characteristic points.

Modified Example

FIGS. 16 and 17 are schematic sectional views illustrating a multilayerceramic capacitor 1C according to a modified example of the secondpreferred embodiment of the present invention. The cross sections shownin FIGS. 16 and 17 correspond to those shown in FIGS. 14 and 15,respectively. The multilayer ceramic capacitor 1C of this modifiedexample will be described below with reference to FIGS. 16 and 17.

As shown in FIGS. 16 and 17, the multilayer ceramic capacitor 1C of thismodified example is different from the multilayer ceramic capacitor 1Bof the second preferred embodiment only in the configuration of theouter portion 6 b 22 of the thickness-direction second outer layersection 6 b 2. More specifically, the outer portion 6 b 22 partiallycurves and protrudes toward the inner portion 6 b 21 of thethickness-direction second outer layer section 6 b 2.

This will be discussed more specifically. As shown in FIG. 16, a portionof the outer portion 6 b 22 which corresponds to the length-directionfirst and second outer layer sections 7 b 1 and 7 b 2 protrudes towardthe inner portion 6 b 21, thus defining curved-and-swelled portions 9 a.As shown in FIG. 17, a portion of the outer portion 6 b 22 whichcorresponds to the width-direction first and second outer layer sections8 b 1 and 8 b 2 protrudes toward the inner portion 6 b 21, thus definingcurved-and-swelled portions 9 b.

The curved-and-swelled portions 9 a and 9 b can be formed easily in thefollowing manner, for example. When a base sheet which will be used asthe ceramic dielectric layer 9 in the outer portion 6 b 22 is attachedto and pressed against a mother block on which the inner portion 6 b 21has already been formed, an elastic member is inserted between thepressure plate and the mother block having this base sheet attachedthereto. By suitably adjusting the thickness and the material of theelastic member, the pressure force to be applied, the thickness of thebase sheet to be attached, or the configuration of the outer surface ofthe mother block, the configurations of the curved-and-swelled portions9 a and 9 b are adjusted.

In the multilayer ceramic capacitor 1C configured as described above,since the interface between the outer portion 6 b 22 and the innerportion 6 b 21 has a non-planar shape, the adhesion force between theouter portion 6 b 22 and the inner portion 6 b 21 is increased, thusmaking it possible to significantly reduce or prevent the occurrence ofdelamination between the outer portion 6 b 22 and the inner portion 6 b21 in advance, compared with a case in which the interface between theouter portion 6 b 22 and the inner portion 6 b 21 has a planar shape. Asa result, with this configuration, it is possible to provide a morereliable multilayer ceramic capacitor.

The multilayer ceramic capacitor 1B of the second preferred embodimentand the multilayer ceramic capacitor 1C of the modified example may alsobe mounted on a mounting member or integrated into a multilayer ceramiccapacitor array, in a manner similar to the multilayer ceramic capacitor1A of the first preferred embodiment of the present invention.

First Verification Test

FIG. 18 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 1 through 7 in a firstverification test.

In the first verification test, the occurrence of cracks in the body ofeach of the multilayer ceramic capacitors after being subjected tofiring and to a thermal shock test was checked by changing thedimensions w1 and w2 of the width-direction first and second outer layersections and by changing the dimension T1 of the multilayer unit.

As shown in FIG. 18, in the first verification test, twenty samples ofeach of seven types of multilayer ceramic capacitors in examples 1through 7 were fabricated. The multilayer ceramic capacitors of examples1 through 7 were all fabricated according to the manufacturing flow ofthe multilayer ceramic capacitor 1A discussed in the first preferredembodiment and were all configured as in the multilayer ceramiccapacitor 1A of the first preferred embodiment. It is noted that all thedimensions in the table shown in FIG. 18 are indicated in terms of thedesign values.

In all of examples 1 through 7, the dimension L0 of the body in thelength direction is about 1220 μm, the dimension L1 of the multilayerunit in the length direction is about 1100 μm, and the dimension W1 ofthe multilayer unit in the width direction is about 640 μm.

In all of examples 1 through 7, the dimension t1 of thethickness-direction first outer layer section is about 40 μm, thedimension t2 of the thickness-direction second outer layer section isabout 140 μm, and the dimensions l1 and l2 of the length-direction firstand second outer layer sections is about 60 μm.

Concerning the dimension T1 of the multilayer unit in the thicknessdirection, the dimension T1 in example 1 is about 640 μm, the dimensionT1 in examples 2 and 3 is about 677 μm, the dimension T1 in example 4 isabout 718 μm, the dimension T1 in examples 5 and 6 is about 736 μm, andthe dimension T1 in example is about 834 μm. In accordance with thedimension T1 of examples 1 through 7, concerning the dimension T0 of thebody in the thickness direction, the dimension T0 in example 1 is about820 μm, the dimension T0 in examples 2 and 3 is about 857 μm, thedimension T0 in example 4 is about 898 μm, the dimension T0 in examples5 and 6 is about 916 μm, and the dimension T0 in example 7 is about 1014μm.

Concerning the dimensions w1 and w2 of the width-direction first andsecond outer layer sections, the dimensions w1 and w2 in examples 1 and2 is about 40 μm, the dimensions w1 and w2 in examples 3 through 5 isabout 52 μm, and the dimensions w1 and w2 in examples 6 and 7 is about60 μm. In accordance with the dimensions w1 and w2 of examples 1 through7, concerning the dimension W0 of the body in the width direction, thedimension W0 in examples 1 and 2 is about 720 μm, the dimension W0 inexamples 3 through 5 is about 744 μm, and the dimension W0 in examples 6and 7 is about 760 μm.

The ratios of the dimensions of the individual sections in examples 1through 7 are indicated in the field “dimension ratios” in the tableshown in FIG. 18. AR1 is a value expressed by T1/(W0−W1).

In all of examples 1 through 7, the thickness x1 of inner electrodelayers included in the multilayer unit subjected to firing is about 0.71μm, and the thickness x2 of ceramic dielectric layers included in themultilayer unit subjected to firing is about 0.89 μm (that is, x1/x2 isabout 0.8). In example 1, the number of inner electrode layers stackedon each other included in the multilayer unit is about 401, while thenumber of ceramic dielectric layers stacked on each other included inthe multilayer unit is about 400. In examples 2 through 7, the number ofinner electrode layers and the number of ceramic dielectric layersstacked on each other included in the multilayer unit are equal to orgreater than those in example 1.

In the first verification test, among the multilayer ceramic capacitorsof examples 1 through 7 fabricated on the basis of the above-describeddesign conditions, concerning ten samples of each of examples 1 through7, after the body was subjected to firing, a W-T cross section havingthe center of the multilayer ceramic capacitor and parallel with both ofthe width direction and the thickness direction of each of the tensamples was exposed by polishing and was observed with an opticalmicroscope so as to check for cracks. The remaining ten samples of eachof examples 1 through 7 were input into a thermal shock tester and weresubjected to a thermal shock cycle. Then, the above-described W-T crosssection was exposed by polishing and was observed with an opticalmicroscope so as to check for cracks.

Concerning the evaluation results of examples 1 through 7, if even onecrack was found in the W-T cross sections of the ten samples of each ofexamples 1 through 7 after the body was subjected to firing, it wasdetermined that cracks occurred (YES), and if none of cracks were found,it was determined that cracks did not occur (NO). Similarly, if even onecrack was found in the W-T cross sections of the ten samples of each ofexamples 1 through 7 after the body was subjected to a thermal shockcycle, it was determined that cracks occurred (YES), and if none ofcracks were found, it was determined that cracks did not occur (NO).

As a result, as indicated in the evaluation results in FIG. 18, inexamples 1, 3, 4, 6, and 7, it was determined that cracks occurredneither in the samples subjected to firing nor the samples subjected toa thermal shock cycle (NO). In example 2, it was determined that cracksoccurred (YES) in both of the samples subjected to firing and thesamples subjected to a thermal shock cycle. In example 5, it wasdetermined that cracks did not occur (NO) in the samples subjected tofiring and it was determined that cracks occurred (YES) in the samplessubjected to a thermal shock cycle.

It is seen from the above-described results that cracks which may occurwhen the body is subjected to firing are effectively reduced orprevented if both of the dimensions w1 and w2 of the width-directionfirst and second outer layer sections are greater than the dimension t1of the thickness-direction first outer layer section (w1>t1 and w2>t1).

It is also seen from the above-described results that cracks which mayoccur when the body is subjected to firing are more effectively reducedor prevented if both of the dimensions w1 and w2 of the width-directionfirst and second outer layer sections are more than about 1.3 times aslarge as the dimension t1 of the thickness-direction first outer layersection (w1/t1>1.3 and w2/t1>1.3).

It is also seen from the above-described results that the occurrence ofcracks in the body under the operating environments, as well as when thebody is subjected to firing, are effectively reduced or prevented ifboth of the dimensions w1 and w2 of the width-direction first and secondouter layer sections are more than about 1.5 times as large as thedimension t1 of the thickness-direction first outer layer section(w1/t1>1.5 and w2/t1>1.5) in a case in which the dimension T1 of themultilayer unit in the thickness direction is about 1.15 times or moreas large as the dimension W1 of the multilayer unit in the widthdirection (T1/W1≧1.15).

It is also seen from the above-described results that the occurrence ofcracks in the body under the operating environments, as well as when thebody is subjected to firing, are effectively reduced or prevented whenthe dimension W0 of the body in the width direction, the dimension T1 ofthe multilayer unit in the thickness direction, and the dimension W1 ofthe multilayer unit in the width direction satisfy the relationshipexpressed by AR1(=T1/(W0−W1))≦6.95.

Second Verification Test

FIG. 19 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 8 through 14 in a secondverification test.

In the second verification test, the occurrence of cracks in the body ofeach of the multilayer ceramic capacitors after being subjected tofiring and to a thermal shock test was checked by changing thedimensions l1 and l2 of length-direction first and second outer layersections and by changing the dimension T1 of a multilayer unit in thethickness direction.

As shown in FIG. 19, in the second verification test, twenty samples ofeach of seven types of multilayer ceramic capacitors of examples 8through 14 were fabricated. The multilayer ceramic capacitors ofexamples 8 through 14 were all fabricated according to the manufacturingflow of the multilayer ceramic capacitor 1A discussed in the firstpreferred embodiment and were all configured as in the multilayerceramic capacitor 1A of the first preferred embodiment. It is noted thatall the dimensions in the table shown in FIG. 19 are indicated in termsof the design values.

In all of examples 8 through 14, the dimension W0 of the body in thewidth direction is about 752 μm, the dimension L1 of the multilayer unitin the length direction is about 1100 μm, and the dimension W1 of themultilayer unit in the width direction is about 640 μm.

In all of examples 8 through 14, the dimension t1 of thethickness-direction first outer layer section is about 40 μm, thedimension t2 of the thickness-direction second outer layer section isabout 140 μm, and the dimensions w1 and w2 of the width-direction firstand second outer layer sections is about 56 μm.

Concerning the dimension T1 of the multilayer unit in the thicknessdirection, the dimension T1 in example 8 is about 640 μm, the dimensionT1 in examples 9 and 10 is about 677 μm, the dimension T1 in example 11is about 718 μm, the dimension T1 in examples 12 and 13 is about 736 μm,and the dimension T1 in example 14 is about 834 μm. In accordance withthe dimension T1 of examples 8 through 14, concerning the dimension T0of the body in the thickness direction, the dimension T0 in example 8 isabout 820 μm, the dimension T0 in examples 9 and 10 is about 857 μm, thedimension T0 in example 11 is about 898 μm, the dimension T0 in examples12 and 13 is about 916 μm, and the dimension T0 in example 14 is about1014 μm.

Concerning the dimensions l1 and l2 of the length-direction first andsecond outer layer sections, the dimensions l1 and l2 in examples 8 and9 is about 40 μm, the dimensions l1 and l2 in examples 10 through 12 isabout 60 μm, and the dimensions l1 and l2 in examples 13 and 14 is about80 μm. In accordance with the dimensions l1 and l2 of examples 8 through14, concerning the dimension L0 of the body in the length direction, thedimension L0 in examples 8 and 9 is about 1180 μm, the dimension L0 inexamples 10 through 12 is about 1220 μm, and the dimension L0 inexamples 13 and 14 is about 1260 μm.

The ratios of the dimensions of the individual sections in examples 8through 14 are indicated in the field “dimension ratios” in the tableshown in FIG. 19. AR2 is a value expressed by T1/(L0−L1).

In all of examples 8 through 14, the thickness x1 of inner electrodelayers included in the multilayer unit subjected to firing is about 0.71μm, and the thickness x2 of ceramic dielectric layers included in themultilayer unit subjected to firing is about 0.89 μm (that is, x1/x2 isabout 0.8). In example 8, the number of inner electrode layers stackedon each other included in the multilayer unit is about 401, while thenumber of ceramic dielectric layers stacked on each other included inthe multilayer unit is about 400. In examples 9 through 14, the numberof inner electrode layers and the number of ceramic dielectric layersstacked on each other included in the multilayer unit are equal to orgreater than those in example 8.

In the second verification test, among the multilayer ceramic capacitorsof examples 8 through 14 fabricated on the basis of the above-describeddesign conditions, concerning ten samples of each of examples 8 through14, after the body was subjected to firing, an L-T cross section havingthe center of the multilayer ceramic capacitor and parallel with both ofthe length direction and the thickness direction of each of the tensamples was exposed by polishing and was observed with an opticalmicroscope so as to check for cracks. The remaining ten samples of eachof examples 8 through 14 were input into a thermal shock tester and weresubjected to a thermal shock cycle. Then, the above-described L-T crosssection was exposed by polishing and was observed with an opticalmicroscope so as to check for cracks.

Concerning the evaluation results of examples 8 through 14, if even onecrack was found in the L-T cross sections of the ten samples of each ofexamples 8 through 14 after the body was subjected to firing, it wasdetermined that cracks occurred (YES), and if none of cracks were found,it was determined that cracks did not occur (NO). Similarly, if even onecrack was found in the L-T cross sections of the ten samples of each ofexamples 8 through 14 after the body was subjected to a thermal shockcycle, it was determined that cracks occurred (YES), and if none ofcracks were found, it was determined that cracks did not occur (NO).

As a result, as indicated in the evaluation results in FIG. 19, inexamples 8, 10, 11, 13, and 14, it was determined that cracks occurredneither in the samples subjected to firing nor the samples subjected toa thermal shock cycle (NO). In example 9, it was determined that cracksoccurred (YES) in both of the samples subjected to firing and thesamples subjected to a thermal shock cycle. In example 12, it wasdetermined that cracks did not occur (NO) in the samples subjected tofiring and it was determined that cracks occurred (YES) in the samplessubjected to a thermal shock cycle.

It is seen from the above-described results that the occurrence ofcracks when the body is subjected to firing is effectively reduced orprevented if both of the dimensions l1 and l2 of the length-directionfirst and second outer layer sections are greater than the dimension t1of the thickness-direction first outer layer section (l1>t1 and l2>t1).

It is also seen from the above-described results that the occurrence ofcracks when the body is subjected to firing is more effectively reducedor prevented if both of the dimensions l1 and l2 of the length-directionfirst and second outer layer sections are more than about 1.5 times aslarge as the dimension t1 of the thickness-direction first outer layersection (l1/t1>1.5 and l2/t1>1.5).

It is also seen from the above-described results that the occurrence ofcracks in the body under the operating environments, as well as when thebody is subjected to firing, are effectively reduced or prevented ifboth of the dimensions l1 and l2 of the length-direction first andsecond outer layer sections are more than twice as large as thedimension t1 of the thickness-direction first outer layer section(l1/t1>2 and l2/t1>2) in a case in which the dimension T1 of themultilayer unit in the thickness direction is about 0.67 times or moreas large as the dimension L1 of the multilayer unit in the lengthdirection (T1/L1≧0.67).

It is also seen from the above-described results that cracks which mayoccur in the body under the operating environments, as well as when thebody is subjected to firing, are effectively reduced or prevented if thedimension L0 of the body in the length direction, the dimension T1 ofthe multilayer unit in the thickness direction, and the dimension L1 ofthe multilayer unit in the length direction satisfy the relationshipexpressed by AR2 (=T1/(L0−L1))≦5.98.

Third Verification Test

FIG. 20 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples 15 through 35 in a thirdverification test.

In the third verification test, multilayer ceramic capacitors includinga thickness-direction second outer layer section constituted by an innerlayer and an outer layer, as discussed in the second preferredembodiment, were fabricated. Then, the occurrence of cracks in the bodyof each of the multilayer ceramic capacitors and the reliability of themultilayer ceramic capacitors after being subjected to firing werechecked by changing the dimensions of the inner layer and the outerlayer in the thickness direction and by changing the content of Si ineach of the inner layer and the outer layer.

As shown in FIG. 20, in the first verification test, twenty samples ofeach of twenty-one types of multilayer ceramic capacitors of examples 15through 35 were fabricated. The multilayer ceramic capacitors ofexamples 15 through 35 were all fabricated according to the non-limitingexample of the manufacturing flow of the multilayer ceramic capacitor 1Adiscussed in the first preferred embodiment and were all configured asin the multilayer ceramic capacitor 1B of the second preferredembodiment. It is noted that all the dimensions in the table shown inFIG. 20 are indicated in terms of the design values.

In all of examples 15 through 35, the dimension t1 of thethickness-direction first outer layer section is about 40 μm, thedimension t2 of the thickness-direction second outer layer section isabout 100 μm, and the dimension T1 of the multilayer unit in thethickness direction is about 620 μm.

In all of examples 15 through 35, the thickness x1 of each of innerelectrode layers included in the multilayer unit subjected to firing isabout 0.8 μm and the number of inner electrode layers stacked on eachother is about 330. In all of examples 15 through 35, the molar ratio ofSi to Ti contained in the ceramic dielectric layer defining the innerlayer (more specifically, the thickness-direction inner layer section,the thickness-direction first outer layer section, and the inner layer)is about 0.013.

Concerning the molar ratio of Si to Ti contained in the ceramicdielectric layer defining the outer layer of the thickness-directionsecond outer layer section, the molar ratio in examples 15 through 21 isabout 0.017, the molar ratio in examples 22 through 28 is about 0.029,and the molar ratio in examples 29 through 35 is about 0.033. Thedifference between the Si content in the ceramic dielectric layerdefining the inner layer and that in the ceramic dielectric layerdefining the outer layer in each of examples 1 through 21 is indicatedin the table shown in FIG. 20.

Concerning the dimension t21 of the inner layer of thethickness-direction second outer layer section, in each of a group ofexamples 15 through 21, a group of examples 22 through 28, and a groupof examples 29 through 35, the dimension t21 sequentially ranges fromabout 10 μm to 70 μm in increments of +10 μm.

Concerning the dimension t22 of the outer layer of thethickness-direction second outer layer section, in each of a group ofexamples 15 through 21, a group of examples 22 through 28, and a groupof examples 29 through 35, the dimension t22 sequentially ranges fromabout 90 μm to 30 μm in increments of −10 μm.

In the third verification test, among the multilayer ceramic capacitorsof examples 15 through 35 fabricated on the basis of the above-describeddesign conditions, concerning ten samples of each of examples 15 through35, after the body was subjected to firing, a W-T cross sectionincluding the center of the multilayer ceramic capacitor and parallelwith both of the width direction and the thickness direction of each ofthe ten samples was exposed by polishing and was observed with anoptical microscope so as to check for cracks. The remaining ten samplesof each of examples 15 through 35 were input into a super-acceleratinglife tester so as to check the reliability of each of the ten samples.In this reliability test, a voltage of 8 V was continuously applied toeach of the samples in an ambient temperature of 150° C., and then, thetime taken for the IR value of each of the samples to reduce to 10 kΩwas measured.

Concerning the evaluation results of examples 15 through 35, if even onecrack was found in the W-T cross sections of the ten samples of each ofexamples 15 through 35 after the body was subjected to firing, it wasdetermined that cracks occurred (YES), and if none of cracks were found,it was determined that cracks did not occur (NO). Similarly, as a resultof conducting the reliability test by inputting the ten samples of eachof examples 15 through 35 into the super-accelerating life tester, ifthe time for the IR value of each of the samples to reduce to 10 kΩ wasten hours or longer, it was determined that the reliability was “GOOD”,and if the time for the IR value of each of the samples to reduce to 10kΩ was shorter than ten hours, it was determined that the reliabilitywas “BAD”.

As a result, as indicated in the evaluation results in FIG. 20, inexamples 15 through 19, 22 through 26, and 29 through in which thedimension t22 of the outer layer of the thickness-direction second outerlayer section is equal to or greater than the dimension t21 of the innerlayer of the thickness-direction second outer layer section, it wasdetermined that cracks occurred neither in the samples subjected tofiring nor in the samples subjected to the reliability test (NO). In allof examples 15 through 19, 22 through 26, and 29 through 33 in which itwas determined that cracks did not occur (NO), it was determined thatthe reliability was “GOOD”, except for example 29 in which the molarratio of Si to Ti contained in the ceramic dielectric layer defining theouter layer was higher than about 0.029 and the dimension t21 of theinner layer was smaller than about 20 μm.

It is seen from the above-described results that cracks which may occurafter the body is subjected to firing are effectively reduced orprevented if the dimension t22 of the outer layer of thethickness-direction second outer layer section is equal to or greaterthan the dimension t21 of the inner layer of the thickness-directionsecond outer layer section. It is also seen from the above-describedresults that, if the dimension t21 of the inner layer of thethickness-direction second outer layer section is about 20 μm orgreater, for example, it is possible to significantly reduce or preventthe occurrence of the short-circuiting of the thickness-direction innerlayer section by maintaining the withstand voltage characteristics ofthe ceramic dielectric layers included in the thickness-direction innerlayer section.

Fourth Verification Test

FIG. 21 is a table illustrating design conditions and evaluation resultsfor multilayer ceramic capacitors of examples through 39 in a fourthverification test. FIG. 22 is a schematic view illustrating a method fordeflecting a wiring board having a multilayer ceramic capacitor mountedthereon in the fourth verification test.

In the fourth verification test, multilayer ceramic capacitors includinga thickness-direction second outer layer section including an innerlayer and an outer layer, as discussed in the second preferredembodiment, were fabricated. Then, the occurrence of cracks in the bodyof each of the multilayer ceramic capacitors after the application of anexternal stress was checked by changing the content of Si in each of theinner layer and the outer layer.

As shown in FIG. 21, in the fourth verification test, ten samples ofeach of four types of multilayer ceramic capacitors of examples 36through 39 were fabricated. The multilayer ceramic capacitors ofexamples 36 through 39 were all fabricated according to themanufacturing flow of the multilayer ceramic capacitor 1A discussed inthe first preferred embodiment and were all configured as in themultilayer ceramic capacitor 1B of the second preferred embodiment. Itis noted that all the dimensions in the table shown in FIG. 21 areindicated in terms of the design values.

In all of examples 36 through 39, the dimension t1 of thethickness-direction first outer layer section is about 100 μm, thedimension t2 of the thickness-direction second outer layer section isabout 100 μm, and the dimension T1 of the multilayer unit in thethickness direction is about 620 μm.

In all of examples 36 through 39, the dimension t21 of the inner layerof the thickness-direction second outer layer section is about 50 μm,and the dimension t22 of the outer layer of the thickness-directionsecond outer layer section is about 50 μm. The thickness x1 of each ofinner electrode layers included in the multilayer unit subjected tofiring is about 0.8 μm and the number of inner electrode layers stackedon each other is about 330.

Concerning the molar ratio of Si to Ti contained in the ceramicdielectric layer defining the inner layer (more specifically, theceramic dielectric layers defining the thickness-direction inner layersection, the thickness-direction first outer layer section, and theinner layer), the molar ratio in examples 36 and 38 is about 0.013, themolar ratio in example is about 0.017, and the molar ratio in example 39is about 0.029.

Concerning the molar ratio of Si to Ti contained in the ceramicdielectric layer defining the outer layer, the molar ratio in examples36 and 37 is about 0.017, and the molar ratio in examples 38 and 39 isabout 0.029. The difference between the Si content in the ceramicdielectric layer defining the inner layer and that in the ceramicdielectric layer defining the outer layer in each of examples 36 through39 is indicated in the table shown in FIG. 21.

In the fourth verification test, concerning the ten samples of themultilayer ceramic capacitors of each of examples through 39 fabricatedon the basis of the above-described design conditions, after themultilayer ceramic capacitors were mounted on respective mountingmembers and an external stress was applied to the mounting members, theoccurrence of cracks reaching an inner electrode layer of each of themultilayer ceramic capacitors was checked.

In this case, the following method was used to apply an external stressto the mounting members, as shown in FIG. 22. A wiring board 101, whichdefines and serves as a mounting member, having the multilayer ceramiccapacitor 1B mounted thereon was disposed such that the multilayerceramic capacitor 1B faced downward. The wiring board 101 was supportedat both sides by support members 301 from below. In this state, apressing tool 300 was vertically pressed against the top surface of thewiring board 101 from upward toward the direction indicated by the arrowDR in FIG. 22 so as to deflect the wiring board 101 downward. Bydeflecting the wiring board 101 with this method, a tensile stress,which is an external stress, was applied to the multilayer ceramiccapacitor 1B via solder and the first and second outer electrodes 5 aand 5 b.

After applying an external stress to the ten samples of the multilayerceramic capacitors of each of examples 22 through 25 by using thismethod, the multilayer ceramic capacitors were demounted from therespective wiring boards. Then, cross sections of the multilayer ceramiccapacitors of the ten samples were exposed by polishing and wereobserved with an optical microscope so as to check for cracks reachingan inner electrode layer.

Concerning the evaluation results of examples 36 through 39, as a resultof observing the cross sections, if even one crack reaching an innerelectrode layer was found in the cross sections of the ten samples ofeach of examples 36 through 39, it was determined that cracks occurred(YES), and if none of cracks reaching an inner electrode layer werefound, it was determined that cracks did not occur (NO).

As a result, as indicated in the evaluation results in FIG. 21, inexamples 36 and 38 in which the Si content in the ceramic dielectriclayer defining the inner layer and that in the ceramic dielectric layerdefining the outer layer differed from each other, it was determinedthat cracks reaching an inner electrode layer did not occur (NO), but onthe other hand, in examples 37 and 39 in which the Si content in theceramic dielectric layer defining the inner layer and that in theceramic dielectric layer defining the outer layer did not differ fromeach other, it was determined that cracks reaching an inner electrodelayer occurred (YES).

It is seen from the above-described results that, by setting the amountof Si content in the ceramic dielectric layer defining the outer layerto be higher than that in the ceramic dielectric layer defining theinner layer, a boundary portion having a higher Si content ratio isprovided in the outer layer. As a result, the development of cracks issignificantly reduced or prevented, or the direction in which cracksdevelop changes, thus preventing cracks from reaching an inner electrodelayer.

Measurement methods for dimensions of individual sections of amultilayer ceramic capacitor will be discussed below.

FIG. 23 illustrates an example of an enlarged image of a cross sectionof a multilayer ceramic capacitor observed with a scanning electronmicroscope (SEM). In FIG. 23, a portion of the second principal surface2 a 2 of the multilayer ceramic capacitor in contact with an embeddingresin 400 is shown.

When measuring the thickness of a ceramic dielectric layer 3 and aconductive layer (inner electrode layer) 4 of a multilayer ceramiccapacitor, the following method is preferably used. In an enlarged imageof a cross section of the multilayer ceramic capacitor observed with aSEM, as shown in FIG. 23, a straight line Lc extending in the thicknessdirection of a body of the multilayer ceramic capacitor and passingthrough the center of the body is drawn. Then, a plurality of straightlines parallel with the straight line Lc are drawn at equal pitches S.The pitch S may be set to be about five to ten times as long as thethickness of the ceramic dielectric layer 3 or that of the conductivelayer 4 to be measured, for example. If, for example, the ceramicdielectric layer 3 having a thickness of about 1 μm is measured, thepitch S preferably is set to be about 5 μm. Then, lines are drawn onboth sides of the straight line Lc. The number of lines drawn on oneside and that on the other side of the straight line Lc are the same.That is, an odd number of lines including the straight line Lc aredrawn. In FIG. 23, an example in which five straight lines La through Leare drawn is shown.

Then, on each of the lines La through Le, the thickness of a ceramicdielectric layer 3 and that of a conductive layer 4 are measured. If, oneach of the straight lines La through Le, a conductive layer 4 ispartially missing and ceramic dielectric layers 3 join each other withthe conductive layer 4 therebetween, or if an enlarged image at aportion to be measured is not clear, the thickness or the distance ismeasured on another straight line separated from the straight line Lc.

When measuring the thickness of a ceramic dielectric layer 3, as shownin FIG. 21, the thickness D1 on the straight line La, the thickness D2on the straight line Lb, the thickness D3 on the straight line Lc, thethickness D4 on the straight line Ld, and the thickness D5 on thestraight line Le are measured, and the average value thereof is set tobe the thickness of the ceramic dielectric layer 3.

When calculating the average thickness of a plurality of ceramicdielectric layers included in a multilayer unit, the thicknesses of atotal of five ceramic dielectric layers constituted by the ceramicdielectric layer positioned substantially at the center of themultilayer unit in the thickness direction and two ceramic dielectriclayers positioned at each of both sides of this ceramic dielectric layerare measured by using the above-described method, and the average valuethereof is set to be the average thickness of the plurality of ceramicdielectric layers included in the multilayer unit.

If the number of ceramic dielectric layers stacked on each other is lessthan five, the thicknesses of all the ceramic dielectric layers aremeasured by using the above-described method, and the average valuethereof is set to be the average thickness of the ceramic dielectriclayers. If the number of conductive layers stacked on each other is lessthan five, the thicknesses of all the conductive layers are measured byusing the above-described method, and the average value thereof is setto be the average thickness of the conductive layers.

An example of the method for measuring the dimensions of thewidth-direction first and second outer layer sections is as follows. AW-T cross section including the center of the body and parallel withboth of the width direction and the thickness direction is exposed bypolishing and is observed with an optical microscope. Then, thewidthwise dimension of a portion adjacent to the conductive layerpositioned closest to the first principal surface and/or the widthwisedimension of a portion adjacent to the conductive layer positionedclosest to the second principal surface are measured.

An example of the method for measuring the dimensions of thelength-direction first and second outer layer sections is as follows. AnL-T cross section including the center of the body and parallel withboth of the length direction and the thickness direction is exposed bypolishing and is observed with an optical microscope. Then, thelongitudinal dimension of a portion adjacent to the conductive layerpositioned closest to the first principal surface and/or thelongitudinal dimension of a portion adjacent to the conductive layerpositioned closest to the second principal surface are measured.

An example of the method for measuring the dimension of the multilayerunit in the width direction is as follows. A W-T cross section includingthe center of the body and parallel with both of the width direction andthe thickness direction is exposed by polishing and is observed with anoptical microscope. Then, the largest dimension of the conductive layerin the width direction is measured.

An example of the method for measuring the dimension of the multilayerunit in the thickness direction is as follows. A W-T cross sectionincluding the center of the body and parallel with both of the widthdirection and the thickness direction is exposed by polishing and isobserved with an optical microscope. Then, the length of the shortestline segment including the center of the body and connecting theconductive layer positioned closest to the first principal surface andthe conductive layer positioned closest to the second principal surfaceis measured as the dimension of the multilayer unit in the thicknessdirection.

An example of the method for measuring the dimensions of thethickness-direction first and second outer layer sections and thedimensions of the inner layer and the outer layer of thethickness-direction second outer layer section is as follows. A W-Tcross section including the center of the body and parallel with both ofthe width direction and the thickness direction is exposed by polishingand is observed with an optical microscope. Then, the thicknesses of thethickness-direction first and second outer layer sections and those ofthe inner layer and the outer layer of the thickness-direction secondouter layer section substantially at the center of the body in the widthdirection are measured.

Analysis methods for the compositions of the individual sections of amultilayer ceramic capacitor will be described below.

Analysis for the composition of components contained in ceramicdielectric layers may be conducted by using inductively coupled plasma(ICP) emission spectrometry or a WDX, for example. If elemental analysisis conducted by using ICP emission spectrometry, a sample is formed intoa powder and is dissolved with an acid. Then, the resulting solution issubjected to ICP emission spectrometry, thereby specifying thecomposition. If elemental analysis is conducted by using a WDX, theabove-described W-T cross section is exposed by polishing the bodyembedded in a resin, and then, the composition is specified by using aWDX attached to a SEM.

The above-described boundary portion of the outer layer having a high Sicontent may be identified as follows. The above-described W-T crosssection is exposed by polishing the body embedded in a resin, and abackscattered electron image of the exposed cross section is captured byusing a SEM and is observed. Alternatively, the boundary portion may beidentified by creating element mapping of the exposed cross section byusing a WDX attached to a SEM and by specifying a portion having a highSi content.

FIG. 24 is a schematic sectional view illustrating a multilayer ceramiccapacitor 1C according to a modification of the second preferredembodiment of the present invention.

As shown in FIG. 24, a body 2 of the multilayer ceramic capacitor 1Cincludes a first outermost layer 4 a, which is the conductive layerdisposed closest to the first principal surface 2 a1 among theconductive layers connected to either one of the first and second outerelectrodes 5 a and 5 b. Also, the body 2 of the multilayer ceramiccapacitor 1C includes a second outermost layer 4 b, which is theconductive layer disposed closest to the second principal surface 2 a2among the conductive layers connected to either one of the first andsecond outer electrodes 5 a and 5 b.

The first extension portion 4 c 1 of the first outermost layer 4 a isinclined toward the second principal surface 2 a 2. With thisconfiguration, it is possible to reduce or prevent the occurrence ofcracks around the boundary between the thickness-direction inner layersection 6 a and the thickness-direction first outer layer section 6 b 1.

The second extension portion 4 c 2 of the second outermost layer 4 b isinclined toward the first principal surface 2 a 1. With thisconfiguration, it is possible to reduce or prevent the occurrence ofcracks around the boundary between the thickness-direction inner layersection 6 a and the thickness-direction second outer layer section 6 b2.

The cracks around the boundary between the thickness-direction innerlayer section 6 a and the thickness-direction second outer layer section6 b 2 is easier to occur than the cracks around the boundary between thethickness-direction inner layer section 6 a and the thickness-directionfirst outer layer section 6 b 1. That is because the thickness-directionsecond outer layer section 6 b 2 is thicker than the thickness-directionfirst outer layer section 6 b 1.

Therefore, an inclination amount C2 is preferably greater than aninclination amount C1 (C2>C1). More preferably, the difference betweenC1 and C2 is preferably greater than a thickness of a ceramic dielectriclayer 3. The inclination amount C1 refers to the distance in thethickness direction T between both ends of the extension portion 4 c 1,while the inclination amount C2 refers to the distance in the thicknessdirection T between both ends of the extension portion 4 c 2.

The inclination amount C2 of the second extension portion 4 c 2 ispreferably greater than a thickness of a portion of a ceramic dielectriclayer 3 adjacent to the second outermost layer 4 b and included in themultilayer unit 10. With this configuration, it is possible to even morereliably reduce or prevent the occurrence of cracks around the boundarybetween the thickness-direction inner layer section 6 a and thethickness-direction second outer layer section 6 b 2.

While preferred embodiments and modified examples thereof according tothe present invention have been described above, it is not intended tobe exhaustive or to limit the present invention to the precise formsdisclosed. It is to be understood that variations and modifications willbe apparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims and theirequivalents.

What is claimed is:
 1. A multilayer ceramic capacitor comprising: a bodyincluding conductive layers and ceramic dielectric layers alternatelystacked on each other in a thickness direction; and a plurality of outerelectrodes disposed on portions of the body; wherein the body includesfirst and second principal surfaces opposing each other in the thicknessdirection, first and second end surfaces opposing each other in a lengthdirection, and first and second side surfaces opposing each other in awidth direction; the plurality of outer electrodes includes a firstouter electrode covering at least the first end surface and a secondouter electrode covering at least the second end surface; some of theconductive layers include a first effective portion and a firstextension portion extending from the first effective portion toward thefirst end surface and connecting to the first outer electrode, andothers of the conductive layers include a second effective portion and asecond extension portion extending from the second effective portiontoward the second end surface and connecting to the second outerelectrode; the body includes a multilayer unit including an effectiveportion defined by the first and second effective portions and portionsof the ceramic dielectric layers stacked therebetween; the body issectioned in the thickness direction into a thickness-direction firstouter layer section that includes one of the ceramic dielectric layersincluding the first principal surface, a thickness-direction secondouter layer section that includes one of the ceramic dielectric layersincluding the second principal surface, and a thickness-direction innerlayer section that includes the multilayer unit and that is disposedbetween the thickness-direction first and second outer layer sections;the body is sectioned in the length direction into a length-directionfirst outer layer section that includes the first extension portions andportions of the ceramic dielectric layers sandwiched by the firstextension portions and that defines the first end surface, alength-direction second outer layer section that includes the secondextension portions and portions of the ceramic dielectric layerssandwiched by the second extension portions and that defines the secondend surface, and a length-direction inner layer section that includesthe multilayer unit and that is disposed between the length-directionfirst and second outer layer sections; the body is sectioned in thewidth direction into a width-direction first outer layer section thatincludes a portion between the first side surface and the multilayerunit, a width-direction second outer layer section that includes aportion between the second side surface and the multilayer unit, and awidth-direction inner layer section that includes the multilayer unitand that is disposed between the width-direction first and second outerlayer sections; a dimension of the thickness-direction second outerlayer section in the thickness direction is greater than a dimension ofthe thickness-direction first outer layer section in the thicknessdirection; the ceramic dielectric layers in the thickness-directioninner layer section and the thickness-direction first and second outerlayer sections contain barium titanate and Si; the thickness-directionsecond outer layer section includes an outer portion which includes thesecond principal surface and an inner portion disposed between thethickness-direction inner layer section and the outer portion; acomposition ratio of Si to Ti in one of the ceramic dielectric layersincluded in the outer portion is higher than a composition ratio of Sito Ti in one of the ceramic dielectric layers included in the innerportion; a boundary portion between the outer portion and the innerportion has a larger Si content than the outer portion; the innerportion has a higher composition ratio of Mn to Ti than the outerportion; and each of minimum dimensions in the length direction of thelength-direction first and second outer layer sections is greater thanboth minimum dimensions in the width direction of the width-directionfirst and second outer layer sections.
 2. The multilayer ceramiccapacitor according to claim 1, wherein the ceramic dielectric layersincluded in the multilayer unit have a higher composition ratio of rareearth element to Ti than the outer portion.
 3. The multilayer ceramiccapacitor according to claim 1, wherein the ceramic dielectric layersincluded in the multilayer unit have a higher composition ratio of Dy toTi than the outer portion.
 4. The multilayer ceramic capacitor accordingto claim 1, wherein a dimension in the thickness direction of the outerportion is greater than a dimension in the thickness direction of theinner portion.
 5. A multilayer ceramic capacitor comprising: a bodyincluding conductive layers and ceramic dielectric layers alternatelystacked on each other in a thickness direction; and a plurality of outerelectrodes disposed on portions of the body; wherein the body includesfirst and second principal surfaces opposing each other in the thicknessdirection, first and second end surfaces opposing each other in a lengthdirection, and first and second side surfaces opposing each other in awidth direction; the plurality of outer electrodes includes a firstouter electrode covering at least the first end surface and a secondouter electrode covering at least the second end surface; some of theconductive layers include a first effective portion and a firstextension portion extending from the first effective portion toward thefirst end surface and connecting to the first outer electrode, andothers of the conductive layers include a second effective portion and asecond extension portion extending from the second effective portiontoward the second end surface and connecting to the second outerelectrode; the body includes a multilayer unit including an effectiveportion defined by the first and second effective portions and portionsof the ceramic dielectric layers stacked therebetween; the body issectioned in the thickness direction into a thickness-direction firstouter layer section that includes one of the ceramic dielectric layersincluding the first principal surface, a thickness-direction secondouter layer section that includes one of the ceramic dielectric layersincluding the second principal surface, and a thickness-direction innerlayer section that includes the multilayer unit and that is disposedbetween the thickness-direction first and second outer layer sections;the body is sectioned in the length direction into a length-directionfirst outer layer section that includes the first extension portions andportions of the ceramic dielectric layers sandwiched by the firstextension portions and that defines the first end surface, alength-direction second outer layer section that includes the secondextension portions and portions of the ceramic dielectric layerssandwiched by the second extension portions and that defines the secondend surface, and a length-direction inner layer section that includesthe multilayer unit and that is disposed between the length-directionfirst and second outer layer sections; the body is sectioned in thewidth direction into a width-direction first outer layer section thatincludes a portion between the first side surface and the multilayerunit, a width-direction second outer layer section that includes aportion between the second side surface and the multilayer unit, and awidth-direction inner layer section that includes multilayer unit andthat is disposed between the width-direction first and second outerlayer sections; a dimension of the thickness-direction second outerlayer section in the thickness direction is greater than a dimension ofthe thickness-direction first outer layer section in the thicknessdirection; the ceramic dielectric layers in the thickness-directioninner layer section and the thickness-direction first and second outerlayer sections contain barium titanate and Si; the thickness-directionsecond outer layer section includes an outer portion which includes thesecond principal surface and an inner portion disposed between thethickness-direction inner layer section and the outer portion; acomposition ratio of Si to Ti in one of the ceramic dielectric layersincluded in the outer portion is higher than a composition ratio of Sito Ti in one of the ceramic dielectric layers included in the innerportion; a boundary portion between the outer portion and the innerportion has a larger Si content than the outer portion; the innerportion has a higher composition ratio of Mn to Ti than the outerportion; each of minimum dimensions in the length direction of thelength-direction first and second outer layer sections is more thanabout 1.15 times as large as both minimum dimensions in the widthdirection of the width-direction first and second outer layer sections.6. The multilayer ceramic capacitor according to claim 5, wherein theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of rare earth element to Ti than the outer portion. 7.The multilayer ceramic capacitor according to claim 5, wherein theceramic dielectric layers included in the multilayer unit have a highercomposition ratio of Dy to Ti than the outer portion.
 8. The multilayerceramic capacitor according to claim 5, wherein a dimension in thethickness direction of the outer portion is greater than a dimension inthe thickness direction of the inner portion.
 9. A multilayer ceramiccapacitor comprising: a body including conductive layers and ceramicdielectric layers alternately stacked on each other in a thicknessdirection; and a plurality of outer electrodes disposed on portions ofthe body; wherein the body includes first and second principal surfacesopposing each other in the thickness direction, first and second endsurfaces opposing each other in a length direction, and first and secondside surfaces opposing each other in a width direction; the plurality ofouter electrodes includes a first outer electrode covering at least thefirst end surface and a second outer electrode covering at least thesecond end surface; some of the conductive layers include a firsteffective portion and a first extension portion extending from the firsteffective portion toward the first end surface and connecting to thefirst outer electrode, and others of the conductive layers include asecond effective portion and a second extension portion extending fromthe second effective portion toward the second end surface andconnecting to the second outer electrode; the body includes a multilayerunit including an effective portion defined by the first and secondeffective portions and portions of the ceramic dielectric layers stackedtherebetween; the body is sectioned in the thickness direction into athickness-direction first outer layer section that includes one of theceramic dielectric layers including the first principal surface, athickness-direction second outer layer section that includes one of theceramic dielectric layers including the second principal surface, and athickness-direction inner layer section that includes the multilayerunit and that is disposed between the thickness-direction first andsecond outer layer sections; the body is sectioned in the lengthdirection into a length-direction first outer layer section thatincludes the first extension portions and portions of the ceramicdielectric layers sandwiched by the first extension portions and thatdefines the first end surface, a length-direction second outer layersection that includes the second extension portions and portions of theceramic dielectric layers sandwiched by the second extension portionsand that defines the second end surface, and a length-direction innerlayer section that includes the multilayer unit and that is disposedbetween the length-direction first and second outer layer sections; thebody is sectioned in the width direction into a width-direction firstouter layer section that includes a portion between the first sidesurface and the multilayer unit, a width-direction second outer layersection that includes a portion between the second side surface and themultilayer unit, and a width-direction inner layer section that includesmultilayer unit and that is disposed between the width-direction firstand second outer layer sections; a dimension of the thickness-directionsecond outer layer section in the thickness direction is greater than adimension of the thickness-direction first outer layer section in thethickness direction; the thickness-direction inner layer section and thethickness-direction first and second outer layer sections contain bariumtitanate and Si; the ceramic dielectric layers included in thethickness-direction second outer layer section includes an outer portionwhich includes the second principal surface and an inner portiondisposed between the thickness-direction inner layer section and theouter portion; a composition ratio of Si to Ti in one of the ceramicdielectric layers included in the outer portion is higher than acomposition ratio of Si to Ti in one of the ceramic dielectric layersincluded in the inner portion; a boundary portion between the outerportion and the inner portion has a larger Si content than the outerportion; the inner portion has a higher composition ratio of Mn to Tithan the outer portion; each of minimum dimensions in the lengthdirection of the length-direction first and second outer layer sectionsis greater than both minimum dimensions in the width direction of thewidth-direction first and second outer layer sections; one of the firstand second extension portions of a first outermost conductive layer ofthe conductive layers that is closest to the first principal surface isinclined toward the second principal surface; one of the first andsecond extension portions of a second outermost conductive layer of theconductive layers that is closest to the second principal surface isinclined toward the first principal surface; and an amount ofinclination of the second outermost conductive layer is greater than anamount of inclination of the first outermost conductive layer.
 10. Themultilayer ceramic capacitor according to claim 9, wherein a differencebetween the amount of inclination of the second outermost conductivelayer and the amount of inclination of the first outermost conductivelayer is greater than a thickness of the dielectric layer stackedbetween the conductive layers.
 11. The multilayer ceramic capacitoraccording to claim 9, wherein the ceramic dielectric layers included inthe multilayer unit have a higher composition ratio of rare earthelement to Ti than the outer portion.
 12. The multilayer ceramiccapacitor according to claim 9, wherein the ceramic dielectric layersincluded in the multilayer unit have a higher composition ratio of Dy toTi than the outer portion.
 13. The multilayer ceramic capacitoraccording to claim 9, wherein a dimension of the outer portion in thethickness direction is greater than a dimension of the inner portion inthe thickness direction.